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	$79.89	9.105%	$87.164	$87.16	$87.15	$87.20
Purchase #2	$185.77	13.244%	$210.3734	$210.37	$210.35	$210.40
Purchase #3	$121.77	4.744%	$127.5468	$127.55	$127.55	$127.50
Purchase #4	$60.32	9.322%	$65.943	$65.94	$65.95	$65.90
Purchase #5	$250.80	9.826%	$275.4436	$275.44	$275.45	$275.40
Purchase #6	$154.97	4.482%	$161.9158	$161.92	$161.90	$161.90
Purchase #7	$36.35	10.406%	$40.1326	$40.13	$40.15	$40.10
7 purchase totals =	$889.87		$968.5192	$968.51	$968.50	$968.40