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	$133.78	10.500%	$147.8269	$147.83	$147.85	$147.80
Purchase #2	$84.77	8.464%	$91.9449	$91.94	$91.95	$91.90
Purchase #3	$7.28	11.766%	$8.1366	$8.14	$8.15	$8.10
Purchase #4	$158.74	5.409%	$167.3262	$167.33	$167.35	$167.30
Purchase #5	$158.52	4.180%	$165.1461	$165.15	$165.15	$165.10
Purchase #6	$33.28	12.728%	$37.5159	$37.52	$37.50	$37.50
Purchase #7	$25.46	13.694%	$28.9465	$28.95	$28.95	$28.90
7 purchase totals =	$601.83		$646.8431	$646.86	$646.90	$646.60