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	$188.37	13.503%	$213.8056	$213.81	$213.80	$213.80
Purchase #2	$123.51	10.552%	$136.5428	$136.54	$136.55	$136.50
Purchase #3	$28.33	13.560%	$32.1715	$32.17	$32.15	$32.20
Purchase #4	$170.80	10.594%	$188.8946	$188.89	$188.90	$188.90
Purchase #5	$51.31	9.517%	$56.1932	$56.19	$56.20	$56.20
Purchase #6	$247.83	12.539%	$278.9054	$278.91	$278.90	$278.90
Purchase #7	$151.32	3.396%	$156.4588	$156.46	$156.45	$156.50
7 purchase totals =	$961.47		$1,062.9719	$1,062.97	$1,062.95	$1,063.00