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	$139.74	5.201%	$147.0079	$147.01	$147.00	$147.00
Purchase #2	$9.67	8.250%	$10.4678	$10.47	$10.45	$10.50
Purchase #3	$66.25	7.813%	$71.4261	$71.43	$71.45	$71.40
Purchase #4	$230.85	8.681%	$250.8901	$250.89	$250.90	$250.90
Purchase #5	$62.68	7.778%	$67.5553	$67.56	$67.55	$67.60
Purchase #6	$100.56	8.341%	$108.9477	$108.95	$108.95	$108.90
Purchase #7	$9.98	11.282%	$11.1059	$11.11	$11.10	$11.10
7 purchase totals =	$619.73		$667.4008	$667.42	$667.40	$667.40