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	$47.99	11.290%	$53.4081	$53.41	$53.40	$53.40
Purchase #2	$172.63	12.583%	$194.352	$194.35	$194.35	$194.40
Purchase #3	$231.69	11.722%	$258.8487	$258.85	$258.85	$258.80
Purchase #4	$59.41	12.444%	$66.803	$66.80	$66.80	$66.80
Purchase #5	$103.40	12.468%	$116.2919	$116.29	$116.30	$116.30
Purchase #6	$220.34	4.564%	$230.3963	$230.40	$230.40	$230.40
Purchase #7	$42.26	9.808%	$46.4049	$46.40	$46.40	$46.40
7 purchase totals =	$877.72		$966.5049	$966.50	$966.50	$966.50