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	$44.77	13.351%	$50.7472	$50.75	$50.75	$50.70
Purchase #2	$185.96	12.653%	$209.4895	$209.49	$209.50	$209.50
Purchase #3	$148.41	3.480%	$153.5747	$153.57	$153.55	$153.60
Purchase #4	$152.27	13.863%	$173.3792	$173.38	$173.40	$173.40
Purchase #5	$59.75	11.158%	$66.4169	$66.42	$66.40	$66.40
Purchase #6	$172.32	11.614%	$192.3332	$192.33	$192.35	$192.30
Purchase #7	$180.25	11.325%	$200.6633	$200.66	$200.65	$200.70
7 purchase totals =	$943.73		$1,046.6040	$1,046.60	$1,046.60	$1,046.60