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	$110.55	8.216%	$119.6328	$119.63	$119.65	$119.60
Purchase #2	$10.71	13.412%	$12.1464	$12.15	$12.15	$12.10
Purchase #3	$130.42	10.803%	$144.5093	$144.51	$144.50	$144.50
Purchase #4	$250.73	13.759%	$285.2279	$285.23	$285.25	$285.20
Purchase #5	$74.55	9.603%	$81.709	$81.71	$81.70	$81.70
Purchase #6	$72.60	5.234%	$76.3999	$76.40	$76.40	$76.40
Purchase #7	$154.82	11.523%	$172.6599	$172.66	$172.65	$172.70
7 purchase totals =	$804.38		$892.2852	$892.29	$892.30	$892.20