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	$34.78	7.310%	$37.3224	$37.32	$37.30	$37.30
Purchase #2	$12.28	12.110%	$13.7671	$13.77	$13.75	$13.80
Purchase #3	$112.45	13.261%	$127.362	$127.36	$127.35	$127.40
Purchase #4	$249.33	10.313%	$275.0434	$275.04	$275.05	$275.00
Purchase #5	$45.29	5.584%	$47.819	$47.82	$47.80	$47.80
Purchase #6	$67.33	13.226%	$76.2351	$76.24	$76.25	$76.20
Purchase #7	$112.94	10.801%	$125.1386	$125.14	$125.15	$125.10
7 purchase totals =	$634.40		$702.6876	$702.69	$702.65	$702.60