Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$170.95	12.706%	$192.6709	$192.67	$192.65	$192.70
Purchase #2	$223.71	4.297%	$233.3228	$233.32	$233.30	$233.30
Purchase #3	$42.89	11.326%	$47.7477	$47.75	$47.75	$47.70
Purchase #4	$238.32	13.627%	$270.7959	$270.80	$270.80	$270.80
Purchase #5	$179.59	11.273%	$199.8352	$199.84	$199.85	$199.80
Purchase #6	$109.29	7.641%	$117.6408	$117.64	$117.65	$117.60
Purchase #7	$117.61	4.626%	$123.0506	$123.05	$123.05	$123.10
7 purchase totals =	$1,082.36		$1,185.0639	$1,185.07	$1,185.05	$1,185.00