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	$235.71	8.478%	$255.6935	$255.69	$255.70	$255.70
Purchase #2	$50.79	9.319%	$55.5231	$55.52	$55.50	$55.50
Purchase #3	$249.69	13.208%	$282.6691	$282.67	$282.65	$282.70
Purchase #4	$95.68	4.268%	$99.7636	$99.76	$99.75	$99.80
Purchase #5	$71.74	8.723%	$77.9979	$78.00	$78.00	$78.00
Purchase #6	$13.61	10.855%	$15.0874	$15.09	$15.10	$15.10
Purchase #7	$238.72	4.239%	$248.8393	$248.84	$248.85	$248.80
7 purchase totals =	$955.94		$1,035.5739	$1,035.57	$1,035.55	$1,035.60