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	$51.97	11.488%	$57.9403	$57.94	$57.95	$57.90
Purchase #2	$35.52	5.451%	$37.4562	$37.46	$37.45	$37.50
Purchase #3	$78.90	13.470%	$89.5278	$89.53	$89.55	$89.50
Purchase #4	$240.91	4.622%	$252.0449	$252.04	$252.05	$252.00
Purchase #5	$58.43	7.675%	$62.9145	$62.91	$62.90	$62.90
Purchase #6	$47.70	5.428%	$50.2892	$50.29	$50.30	$50.30
Purchase #7	$218.54	7.634%	$235.2233	$235.22	$235.20	$235.20
7 purchase totals =	$731.97		$785.3962	$785.39	$785.40	$785.30