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	$170.28	10.571%	$188.2803	$188.28	$188.30	$188.30
Purchase #2	$49.75	10.396%	$54.922	$54.92	$54.90	$54.90
Purchase #3	$185.84	12.183%	$208.4809	$208.48	$208.50	$208.50
Purchase #4	$159.37	6.503%	$169.7338	$169.73	$169.75	$169.70
Purchase #5	$185.85	13.170%	$210.3264	$210.33	$210.35	$210.30
Purchase #6	$145.81	4.258%	$152.0186	$152.02	$152.00	$152.00
Purchase #7	$166.80	3.811%	$173.1567	$173.16	$173.15	$173.20
7 purchase totals =	$1,063.70		$1,156.9187	$1,156.92	$1,156.95	$1,156.90