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	$10.90	10.552%	$12.0502	$12.05	$12.05	$12.10
Purchase #2	$216.72	11.707%	$242.0914	$242.09	$242.10	$242.10
Purchase #3	$126.41	10.300%	$139.4302	$139.43	$139.45	$139.40
Purchase #4	$89.67	5.867%	$94.9309	$94.93	$94.95	$94.90
Purchase #5	$247.51	13.584%	$281.1318	$281.13	$281.15	$281.10
Purchase #6	$87.31	3.442%	$90.3152	$90.32	$90.30	$90.30
Purchase #7	$186.48	12.519%	$209.8254	$209.83	$209.85	$209.80
7 purchase totals =	$965.00		$1,069.7751	$1,069.78	$1,069.85	$1,069.70