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	$153.37	3.559%	$158.8284	$158.83	$158.85	$158.80
Purchase #2	$173.84	13.659%	$197.5848	$197.58	$197.60	$197.60
Purchase #3	$133.56	4.485%	$139.5502	$139.55	$139.55	$139.60
Purchase #4	$208.39	3.413%	$215.5024	$215.50	$215.50	$215.50
Purchase #5	$159.41	10.790%	$176.6103	$176.61	$176.60	$176.60
Purchase #6	$244.73	12.552%	$275.4485	$275.45	$275.45	$275.40
Purchase #7	$70.41	3.556%	$72.9138	$72.91	$72.90	$72.90
7 purchase totals =	$1,143.71		$1,236.4384	$1,236.43	$1,236.45	$1,236.40