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	$48.69	10.584%	$53.8433	$53.84	$53.85	$53.80
Purchase #2	$47.96	9.121%	$52.3344	$52.33	$52.35	$52.30
Purchase #3	$146.90	3.468%	$151.9945	$151.99	$152.00	$152.00
Purchase #4	$231.44	10.553%	$255.8639	$255.86	$255.85	$255.90
Purchase #5	$33.52	11.139%	$37.2538	$37.25	$37.25	$37.30
Purchase #6	$91.81	8.625%	$99.7286	$99.73	$99.75	$99.70
Purchase #7	$85.81	10.851%	$95.1212	$95.12	$95.10	$95.10
7 purchase totals =	$686.13		$746.1397	$746.12	$746.15	$746.10