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	$32.38	9.673%	$35.5121	$35.51	$35.50	$35.50
Purchase #2	$205.84	12.159%	$230.8681	$230.87	$230.85	$230.90
Purchase #3	$162.72	13.141%	$184.103	$184.10	$184.10	$184.10
Purchase #4	$56.79	8.634%	$61.6932	$61.69	$61.70	$61.70
Purchase #5	$185.82	6.606%	$198.0953	$198.10	$198.10	$198.10
Purchase #6	$35.42	10.482%	$39.1327	$39.13	$39.15	$39.10
Purchase #7	$140.48	10.567%	$155.3245	$155.32	$155.30	$155.30
7 purchase totals =	$819.45		$904.7289	$904.72	$904.70	$904.70