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	$11.45	8.541%	$12.4279	$12.43	$12.45	$12.40
Purchase #2	$54.28	12.576%	$61.1063	$61.11	$61.10	$61.10
Purchase #3	$67.65	6.580%	$72.1014	$72.10	$72.10	$72.10
Purchase #4	$202.90	11.122%	$225.4665	$225.47	$225.45	$225.50
Purchase #5	$58.96	12.384%	$66.2616	$66.26	$66.25	$66.30
Purchase #6	$64.42	4.141%	$67.0876	$67.09	$67.10	$67.10
Purchase #7	$22.48	6.781%	$24.0044	$24.00	$24.00	$24.00
7 purchase totals =	$482.14		$528.4557	$528.46	$528.45	$528.50