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	$189.73	4.829%	$198.8921	$198.89	$198.90	$198.90
Purchase #2	$127.26	11.301%	$141.6417	$141.64	$141.65	$141.60
Purchase #3	$231.39	10.746%	$256.2552	$256.26	$256.25	$256.30
Purchase #4	$152.47	13.430%	$172.9467	$172.95	$172.95	$172.90
Purchase #5	$67.29	5.593%	$71.0535	$71.05	$71.05	$71.10
Purchase #6	$132.51	6.345%	$140.9178	$140.92	$140.90	$140.90
Purchase #7	$212.40	13.434%	$240.9338	$240.93	$240.95	$240.90
7 purchase totals =	$1,113.05		$1,222.6408	$1,222.64	$1,222.65	$1,222.60