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	$92.34	4.179%	$96.1989	$96.20	$96.20	$96.20
Purchase #2	$143.64	12.747%	$161.9498	$161.95	$161.95	$161.90
Purchase #3	$163.42	5.201%	$171.9195	$171.92	$171.90	$171.90
Purchase #4	$37.55	13.155%	$42.4897	$42.49	$42.50	$42.50
Purchase #5	$99.39	12.228%	$111.5434	$111.54	$111.55	$111.50
Purchase #6	$162.61	8.643%	$176.6644	$176.66	$176.65	$176.70
Purchase #7	$235.54	11.351%	$262.2761	$262.28	$262.30	$262.30
7 purchase totals =	$934.49		$1,023.0418	$1,023.04	$1,023.05	$1,023.00