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	$55.60	10.365%	$61.3629	$61.36	$61.35	$61.40
Purchase #2	$93.89	13.458%	$106.5257	$106.53	$106.55	$106.50
Purchase #3	$223.88	12.344%	$251.5157	$251.52	$251.50	$251.50
Purchase #4	$21.80	5.235%	$22.9412	$22.94	$22.95	$22.90
Purchase #5	$19.37	11.711%	$21.6384	$21.64	$21.65	$21.60
Purchase #6	$77.98	9.214%	$85.1651	$85.17	$85.15	$85.20
Purchase #7	$134.87	11.456%	$150.3207	$150.32	$150.30	$150.30
7 purchase totals =	$627.39		$699.4697	$699.48	$699.45	$699.40