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	$83.92	13.356%	$95.1284	$95.13	$95.15	$95.10
Purchase #2	$50.43	10.482%	$55.7161	$55.72	$55.70	$55.70
Purchase #3	$216.63	10.694%	$239.7964	$239.80	$239.80	$239.80
Purchase #4	$88.28	10.408%	$97.4682	$97.47	$97.45	$97.50
Purchase #5	$178.78	12.159%	$200.5179	$200.52	$200.50	$200.50
Purchase #6	$16.85	11.454%	$18.78	$18.78	$18.80	$18.80
Purchase #7	$28.67	13.482%	$32.5353	$32.54	$32.55	$32.50
7 purchase totals =	$663.56		$739.9423	$739.96	$739.95	$739.90