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	$113.40	4.390%	$118.3783	$118.38	$118.40	$118.40
Purchase #2	$37.72	8.826%	$41.0492	$41.05	$41.05	$41.00
Purchase #3	$195.74	5.105%	$205.7325	$205.73	$205.75	$205.70
Purchase #4	$37.58	11.830%	$42.0257	$42.03	$42.05	$42.00
Purchase #5	$69.30	12.192%	$77.7491	$77.75	$77.75	$77.70
Purchase #6	$113.49	4.111%	$118.1556	$118.16	$118.15	$118.20
Purchase #7	$89.46	3.400%	$92.5016	$92.50	$92.50	$92.50
7 purchase totals =	$656.69		$695.5920	$695.60	$695.65	$695.50