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	$193.50	12.186%	$217.0799	$217.08	$217.10	$217.10
Purchase #2	$60.95	10.508%	$67.3546	$67.35	$67.35	$67.40
Purchase #3	$197.68	6.171%	$209.8788	$209.88	$209.90	$209.90
Purchase #4	$78.69	4.575%	$82.2901	$82.29	$82.30	$82.30
Purchase #5	$118.39	8.777%	$128.7811	$128.78	$128.80	$128.80
Purchase #6	$161.58	4.240%	$168.431	$168.43	$168.45	$168.40
Purchase #7	$247.28	11.249%	$275.0965	$275.10	$275.10	$275.10
7 purchase totals =	$1,058.07		$1,148.9120	$1,148.91	$1,149.00	$1,149.00