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	$32.77	8.754%	$35.6387	$35.64	$35.65	$35.60
Purchase #2	$168.67	13.686%	$191.7542	$191.75	$191.75	$191.80
Purchase #3	$153.95	7.198%	$165.0313	$165.03	$165.05	$165.00
Purchase #4	$138.82	5.223%	$146.0706	$146.07	$146.05	$146.10
Purchase #5	$88.51	12.538%	$99.6074	$99.61	$99.60	$99.60
Purchase #6	$134.59	9.178%	$146.9427	$146.94	$146.95	$146.90
Purchase #7	$189.84	9.604%	$208.0722	$208.07	$208.05	$208.10
7 purchase totals =	$907.15		$993.1171	$993.11	$993.10	$993.10