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	$62.89	3.122%	$64.8534	$64.85	$64.85	$64.90
Purchase #2	$124.38	3.657%	$128.9286	$128.93	$128.95	$128.90
Purchase #3	$22.72	12.485%	$25.5566	$25.56	$25.55	$25.60
Purchase #4	$37.94	12.434%	$42.6575	$42.66	$42.65	$42.70
Purchase #5	$93.55	12.791%	$105.516	$105.52	$105.50	$105.50
Purchase #6	$190.53	5.423%	$200.8624	$200.86	$200.85	$200.90
Purchase #7	$70.29	9.441%	$76.9261	$76.93	$76.95	$76.90
7 purchase totals =	$602.30		$645.3006	$645.31	$645.30	$645.40