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	$156.72	10.141%	$172.613	$172.61	$172.60	$172.60
Purchase #2	$185.81	12.325%	$208.7111	$208.71	$208.70	$208.70
Purchase #3	$137.60	11.244%	$153.0717	$153.07	$153.05	$153.10
Purchase #4	$188.95	4.188%	$196.8632	$196.86	$196.85	$196.90
Purchase #5	$176.48	6.165%	$187.36	$187.36	$187.35	$187.40
Purchase #6	$35.68	10.293%	$39.3525	$39.35	$39.35	$39.40
Purchase #7	$143.80	6.800%	$153.5784	$153.58	$153.60	$153.60
7 purchase totals =	$1,025.04		$1,111.5499	$1,111.54	$1,111.50	$1,111.70