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	$99.25	4.369%	$103.5862	$103.59	$103.60	$103.60
Purchase #2	$226.67	4.869%	$237.7066	$237.71	$237.70	$237.70
Purchase #3	$5.47	7.455%	$5.8778	$5.88	$5.90	$5.90
Purchase #4	$237.81	3.118%	$245.2249	$245.22	$245.20	$245.20
Purchase #5	$69.52	4.818%	$72.8695	$72.87	$72.85	$72.90
Purchase #6	$106.67	12.453%	$119.9536	$119.95	$119.95	$120.00
Purchase #7	$105.88	10.333%	$116.8206	$116.82	$116.80	$116.80
7 purchase totals =	$851.27		$902.0392	$902.04	$902.00	$902.10