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	$235.44	11.762%	$263.1325	$263.13	$263.15	$263.10
Purchase #2	$114.78	10.167%	$126.4497	$126.45	$126.45	$126.40
Purchase #3	$93.42	10.611%	$103.3328	$103.33	$103.35	$103.30
Purchase #4	$250.69	11.484%	$279.4792	$279.48	$279.50	$279.50
Purchase #5	$71.76	3.644%	$74.3749	$74.37	$74.35	$74.40
Purchase #6	$33.67	11.168%	$37.4303	$37.43	$37.45	$37.40
Purchase #7	$40.36	10.343%	$44.5344	$44.53	$44.55	$44.50
7 purchase totals =	$840.12		$928.7338	$928.72	$928.80	$928.60