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	$189.40	6.622%	$201.9421	$201.94	$201.95	$201.90
Purchase #2	$59.52	11.487%	$66.3571	$66.36	$66.35	$66.40
Purchase #3	$10.25	10.366%	$11.3125	$11.31	$11.30	$11.30
Purchase #4	$156.57	10.477%	$172.9738	$172.97	$172.95	$173.00
Purchase #5	$59.67	13.738%	$67.8675	$67.87	$67.85	$67.90
Purchase #6	$232.98	10.273%	$256.914	$256.91	$256.90	$256.90
Purchase #7	$204.67	12.309%	$229.8628	$229.86	$229.85	$229.90
7 purchase totals =	$913.06		$1,007.2298	$1,007.22	$1,007.15	$1,007.30