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	$65.65	8.858%	$71.4653	$71.47	$71.45	$71.50
Purchase #2	$208.69	6.784%	$222.8475	$222.85	$222.85	$222.80
Purchase #3	$165.83	4.749%	$173.7053	$173.71	$173.70	$173.70
Purchase #4	$79.48	3.742%	$82.4541	$82.45	$82.45	$82.50
Purchase #5	$37.99	11.391%	$42.3174	$42.32	$42.30	$42.30
Purchase #6	$39.30	12.805%	$44.3324	$44.33	$44.35	$44.30
Purchase #7	$94.70	7.421%	$101.7277	$101.73	$101.75	$101.70
7 purchase totals =	$691.64		$738.8497	$738.86	$738.85	$738.80