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	$195.91	13.866%	$223.0749	$223.07	$223.05	$223.10
Purchase #2	$30.58	8.231%	$33.097	$33.10	$33.10	$33.10
Purchase #3	$114.67	11.191%	$127.5027	$127.50	$127.50	$127.50
Purchase #4	$113.43	12.616%	$127.7403	$127.74	$127.75	$127.70
Purchase #5	$44.91	6.811%	$47.9688	$47.97	$47.95	$48.00
Purchase #6	$77.83	7.861%	$83.9482	$83.95	$83.95	$83.90
Purchase #7	$36.79	9.588%	$40.3174	$40.32	$40.30	$40.30
7 purchase totals =	$614.12		$683.6493	$683.65	$683.60	$683.60