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	$134.59	10.181%	$148.2926	$148.29	$148.30	$148.30
Purchase #2	$240.50	4.526%	$251.385	$251.39	$251.40	$251.40
Purchase #3	$174.35	10.391%	$192.4667	$192.47	$192.45	$192.50
Purchase #4	$43.58	3.498%	$45.1044	$45.10	$45.10	$45.10
Purchase #5	$127.62	13.504%	$144.8538	$144.85	$144.85	$144.90
Purchase #6	$57.32	12.597%	$64.5406	$64.54	$64.55	$64.50
Purchase #7	$120.63	3.578%	$124.9461	$124.95	$124.95	$124.90
7 purchase totals =	$898.59		$971.5892	$971.59	$971.60	$971.60