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	$31.26	7.242%	$33.5238	$33.52	$33.50	$33.50
Purchase #2	$160.73	13.612%	$182.6086	$182.61	$182.60	$182.60
Purchase #3	$250.43	9.647%	$274.589	$274.59	$274.60	$274.60
Purchase #4	$27.27	11.761%	$30.4772	$30.48	$30.50	$30.50
Purchase #5	$210.85	9.204%	$230.2566	$230.26	$230.25	$230.30
Purchase #6	$196.94	10.152%	$216.9333	$216.93	$216.95	$216.90
Purchase #7	$176.94	7.443%	$190.1096	$190.11	$190.10	$190.10
7 purchase totals =	$1,054.42		$1,158.4981	$1,158.50	$1,158.50	$1,158.50