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	$127.43	7.116%	$136.4979	$136.50	$136.50	$136.50
Purchase #2	$135.86	7.735%	$146.3688	$146.37	$146.35	$146.40
Purchase #3	$175.51	11.804%	$196.2272	$196.23	$196.25	$196.20
Purchase #4	$112.46	11.599%	$125.5042	$125.50	$125.50	$125.50
Purchase #5	$24.94	6.530%	$26.5686	$26.57	$26.55	$26.60
Purchase #6	$195.99	6.407%	$208.5471	$208.55	$208.55	$208.50
Purchase #7	$161.30	6.714%	$172.1297	$172.13	$172.15	$172.10
7 purchase totals =	$933.49		$1,011.8435	$1,011.85	$1,011.85	$1,011.80