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	$93.53	4.225%	$97.4816	$97.48	$97.50	$97.50
Purchase #2	$14.50	9.164%	$15.8288	$15.83	$15.85	$15.80
Purchase #3	$137.33	8.121%	$148.4826	$148.48	$148.50	$148.50
Purchase #4	$219.35	12.872%	$247.5847	$247.58	$247.60	$247.60
Purchase #5	$196.30	13.310%	$222.4275	$222.43	$222.45	$222.40
Purchase #6	$81.66	13.314%	$92.5322	$92.53	$92.55	$92.50
Purchase #7	$10.90	7.153%	$11.6797	$11.68	$11.70	$11.70
7 purchase totals =	$753.57		$836.0171	$836.01	$836.15	$836.00