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	$197.43	12.384%	$221.8797	$221.88	$221.90	$221.90
Purchase #2	$240.33	3.469%	$248.667	$248.67	$248.65	$248.70
Purchase #3	$235.57	12.324%	$264.6016	$264.60	$264.60	$264.60
Purchase #4	$137.79	11.679%	$153.8825	$153.88	$153.90	$153.90
Purchase #5	$142.33	11.143%	$158.1898	$158.19	$158.20	$158.20
Purchase #6	$133.29	11.391%	$148.4731	$148.47	$148.45	$148.50
Purchase #7	$25.35	7.140%	$27.16	$27.16	$27.15	$27.20
7 purchase totals =	$1,112.09		$1,222.8537	$1,222.85	$1,222.85	$1,223.00