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	$206.46	7.790%	$222.5432	$222.54	$222.55	$222.50
Purchase #2	$115.75	13.375%	$131.2316	$131.23	$131.25	$131.20
Purchase #3	$9.31	13.684%	$10.584	$10.58	$10.60	$10.60
Purchase #4	$81.80	8.164%	$88.4782	$88.48	$88.50	$88.50
Purchase #5	$12.68	13.827%	$14.4333	$14.43	$14.45	$14.40
Purchase #6	$100.50	3.197%	$103.713	$103.71	$103.70	$103.70
Purchase #7	$148.81	13.578%	$169.0154	$169.02	$169.00	$169.00
7 purchase totals =	$675.31		$739.9987	$739.99	$740.05	$739.90