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	$139.27	3.854%	$144.6375	$144.64	$144.65	$144.60
Purchase #2	$111.45	11.322%	$124.0684	$124.07	$124.05	$124.10
Purchase #3	$158.81	13.414%	$180.1128	$180.11	$180.10	$180.10
Purchase #4	$119.95	8.481%	$130.123	$130.12	$130.10	$130.10
Purchase #5	$82.37	9.486%	$90.1836	$90.18	$90.20	$90.20
Purchase #6	$236.78	10.847%	$262.4635	$262.46	$262.45	$262.50
Purchase #7	$189.53	4.774%	$198.5782	$198.58	$198.60	$198.60
7 purchase totals =	$1,038.16		$1,130.1670	$1,130.16	$1,130.15	$1,130.20