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	$169.66	13.296%	$192.218	$192.22	$192.20	$192.20
Purchase #2	$150.73	9.250%	$164.6725	$164.67	$164.65	$164.70
Purchase #3	$149.55	12.790%	$168.6774	$168.68	$168.70	$168.70
Purchase #4	$164.70	4.682%	$172.4113	$172.41	$172.40	$172.40
Purchase #5	$230.67	8.545%	$250.3808	$250.38	$250.40	$250.40
Purchase #6	$248.58	5.764%	$262.9082	$262.91	$262.90	$262.90
Purchase #7	$38.38	3.256%	$39.6297	$39.63	$39.65	$39.60
7 purchase totals =	$1,152.27		$1,250.8979	$1,250.90	$1,250.90	$1,250.90