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	$69.54	11.254%	$77.366	$77.37	$77.35	$77.40
Purchase #2	$145.45	10.147%	$160.2088	$160.21	$160.20	$160.20
Purchase #3	$185.38	3.199%	$191.3103	$191.31	$191.30	$191.30
Purchase #4	$100.58	8.371%	$108.9996	$109.00	$109.00	$109.00
Purchase #5	$236.25	8.557%	$256.4659	$256.47	$256.45	$256.50
Purchase #6	$85.72	3.707%	$88.8976	$88.90	$88.90	$88.90
Purchase #7	$65.71	10.317%	$72.4893	$72.49	$72.50	$72.50
7 purchase totals =	$888.63		$955.7375	$955.75	$955.70	$955.80