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	$128.71	13.636%	$146.2609	$146.26	$146.25	$146.30
Purchase #2	$200.62	12.399%	$225.4949	$225.49	$225.50	$225.50
Purchase #3	$179.46	7.845%	$193.5386	$193.54	$193.55	$193.50
Purchase #4	$216.71	3.211%	$223.6686	$223.67	$223.65	$223.70
Purchase #5	$97.89	13.443%	$111.0494	$111.05	$111.05	$111.00
Purchase #6	$135.34	13.677%	$153.8505	$153.85	$153.85	$153.90
Purchase #7	$234.58	9.296%	$256.3866	$256.39	$256.40	$256.40
7 purchase totals =	$1,193.31		$1,310.2495	$1,310.25	$1,310.25	$1,310.30