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	$66.32	13.168%	$75.053	$75.05	$75.05	$75.10
Purchase #2	$159.96	4.119%	$166.5488	$166.55	$166.55	$166.50
Purchase #3	$69.94	12.495%	$78.679	$78.68	$78.70	$78.70
Purchase #4	$199.29	11.792%	$222.7903	$222.79	$222.80	$222.80
Purchase #5	$195.40	10.680%	$216.2687	$216.27	$216.25	$216.30
Purchase #6	$89.98	11.553%	$100.3754	$100.38	$100.40	$100.40
Purchase #7	$153.43	13.665%	$174.3962	$174.40	$174.40	$174.40
7 purchase totals =	$934.32		$1,034.1114	$1,034.12	$1,034.15	$1,034.20