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	$67.74	5.401%	$71.3986	$71.40	$71.40	$71.40
Purchase #2	$9.67	4.319%	$10.0876	$10.09	$10.10	$10.10
Purchase #3	$73.61	6.826%	$78.6346	$78.63	$78.65	$78.60
Purchase #4	$97.91	5.271%	$103.0708	$103.07	$103.05	$103.10
Purchase #5	$164.73	5.512%	$173.8099	$173.81	$173.80	$173.80
Purchase #6	$125.47	11.411%	$139.7874	$139.79	$139.80	$139.80
Purchase #7	$95.43	8.669%	$103.7028	$103.70	$103.70	$103.70
7 purchase totals =	$634.56		$680.4917	$680.49	$680.50	$680.50