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	$91.26	13.590%	$103.6622	$103.66	$103.65	$103.70
Purchase #2	$108.35	3.146%	$111.7587	$111.76	$111.75	$111.80
Purchase #3	$91.29	10.443%	$100.8234	$100.82	$100.80	$100.80
Purchase #4	$181.57	6.562%	$193.4846	$193.48	$193.50	$193.50
Purchase #5	$138.69	11.185%	$154.2025	$154.20	$154.20	$154.20
Purchase #6	$133.86	10.434%	$147.827	$147.83	$147.85	$147.80
Purchase #7	$173.65	10.112%	$191.2095	$191.21	$191.20	$191.20
7 purchase totals =	$918.67		$1,002.9679	$1,002.96	$1,002.95	$1,003.00