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	$54.30	10.363%	$59.9271	$59.93	$59.95	$59.90
Purchase #2	$72.52	6.223%	$77.0329	$77.03	$77.05	$77.00
Purchase #3	$242.54	13.318%	$274.8415	$274.84	$274.85	$274.80
Purchase #4	$124.72	4.512%	$130.3474	$130.35	$130.35	$130.30
Purchase #5	$145.58	7.111%	$155.9322	$155.93	$155.95	$155.90
Purchase #6	$165.39	3.648%	$171.4234	$171.42	$171.40	$171.40
Purchase #7	$32.78	6.622%	$34.9507	$34.95	$34.95	$35.00
7 purchase totals =	$837.83		$904.4552	$904.45	$904.50	$904.30