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	$85.54	11.182%	$95.1051	$95.11	$95.10	$95.10
Purchase #2	$209.35	6.262%	$222.4595	$222.46	$222.45	$222.50
Purchase #3	$164.74	11.837%	$184.2403	$184.24	$184.25	$184.20
Purchase #4	$74.64	9.733%	$81.9047	$81.90	$81.90	$81.90
Purchase #5	$215.98	3.332%	$223.1765	$223.18	$223.20	$223.20
Purchase #6	$16.54	6.193%	$17.5643	$17.56	$17.55	$17.60
Purchase #7	$239.63	12.811%	$270.329	$270.33	$270.35	$270.30
7 purchase totals =	$1,006.42		$1,094.7794	$1,094.78	$1,094.80	$1,094.80