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	$67.66	13.243%	$76.6202	$76.62	$76.60	$76.60
Purchase #2	$9.93	10.199%	$10.9428	$10.94	$10.95	$10.90
Purchase #3	$70.62	13.726%	$80.3133	$80.31	$80.30	$80.30
Purchase #4	$32.66	5.548%	$34.472	$34.47	$34.45	$34.50
Purchase #5	$214.70	3.229%	$221.6327	$221.63	$221.65	$221.60
Purchase #6	$201.57	3.217%	$208.0545	$208.05	$208.05	$208.10
Purchase #7	$33.43	12.143%	$37.4894	$37.49	$37.50	$37.50
7 purchase totals =	$630.57		$669.5249	$669.51	$669.50	$669.50