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	$151.40	11.118%	$168.2327	$168.23	$168.25	$168.20
Purchase #2	$114.80	8.763%	$124.8599	$124.86	$124.85	$124.90
Purchase #3	$61.80	9.224%	$67.5004	$67.50	$67.50	$67.50
Purchase #4	$161.60	8.436%	$175.2326	$175.23	$175.25	$175.20
Purchase #5	$216.41	7.824%	$233.3419	$233.34	$233.35	$233.30
Purchase #6	$85.89	6.754%	$91.691	$91.69	$91.70	$91.70
Purchase #7	$230.91	11.268%	$256.9289	$256.93	$256.95	$256.90
7 purchase totals =	$1,022.81		$1,117.7874	$1,117.78	$1,117.85	$1,117.70