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	$159.48	3.568%	$165.1702	$165.17	$165.15	$165.20
Purchase #2	$152.66	8.344%	$165.398	$165.40	$165.40	$165.40
Purchase #3	$196.77	3.222%	$203.1099	$203.11	$203.10	$203.10
Purchase #4	$87.64	4.450%	$91.54	$91.54	$91.55	$91.50
Purchase #5	$205.85	10.532%	$227.5301	$227.53	$227.55	$227.50
Purchase #6	$190.57	3.103%	$196.4834	$196.48	$196.50	$196.50
Purchase #7	$85.94	13.169%	$97.2574	$97.26	$97.25	$97.30
7 purchase totals =	$1,078.91		$1,146.4890	$1,146.49	$1,146.50	$1,146.50