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	$106.83	7.532%	$114.8764	$114.88	$114.90	$114.90
Purchase #2	$162.33	12.855%	$183.1975	$183.20	$183.20	$183.20
Purchase #3	$241.82	11.427%	$269.4528	$269.45	$269.45	$269.50
Purchase #4	$21.50	4.713%	$22.5133	$22.51	$22.50	$22.50
Purchase #5	$126.62	10.118%	$139.4314	$139.43	$139.45	$139.40
Purchase #6	$230.67	13.807%	$262.5186	$262.52	$262.50	$262.50
Purchase #7	$247.83	11.312%	$275.8645	$275.86	$275.85	$275.90
7 purchase totals =	$1,137.60		$1,267.8545	$1,267.85	$1,267.85	$1,267.90