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	$146.51	3.516%	$151.6613	$151.66	$151.65	$151.70
Purchase #2	$235.56	12.347%	$264.6446	$264.64	$264.65	$264.60
Purchase #3	$20.43	5.328%	$21.5185	$21.52	$21.50	$21.50
Purchase #4	$39.69	6.539%	$42.2853	$42.29	$42.30	$42.30
Purchase #5	$187.99	10.809%	$208.3098	$208.31	$208.30	$208.30
Purchase #6	$216.68	9.709%	$237.7175	$237.72	$237.70	$237.70
Purchase #7	$156.39	6.601%	$166.7133	$166.71	$166.70	$166.70
7 purchase totals =	$1,003.25		$1,092.8503	$1,092.85	$1,092.80	$1,092.80