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	$92.42	13.680%	$105.0631	$105.06	$105.05	$105.10
Purchase #2	$225.47	11.563%	$251.5411	$251.54	$251.55	$251.50
Purchase #3	$227.54	10.272%	$250.9129	$250.91	$250.90	$250.90
Purchase #4	$237.25	3.276%	$245.0223	$245.02	$245.00	$245.00
Purchase #5	$245.41	12.494%	$276.0715	$276.07	$276.05	$276.10
Purchase #6	$153.82	8.534%	$166.947	$166.95	$166.95	$166.90
Purchase #7	$72.37	13.399%	$82.0669	$82.07	$82.05	$82.10
7 purchase totals =	$1,254.28		$1,377.6248	$1,377.62	$1,377.55	$1,377.60