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	$59.41	3.130%	$61.2695	$61.27	$61.25	$61.30
Purchase #2	$91.43	4.714%	$95.74	$95.74	$95.75	$95.70
Purchase #3	$161.27	13.800%	$183.5253	$183.53	$183.55	$183.50
Purchase #4	$141.57	11.600%	$157.9921	$157.99	$158.00	$158.00
Purchase #5	$151.67	13.441%	$172.056	$172.06	$172.05	$172.10
Purchase #6	$11.34	13.335%	$12.8522	$12.85	$12.85	$12.90
Purchase #7	$121.77	12.665%	$137.1922	$137.19	$137.20	$137.20
7 purchase totals =	$738.46		$820.6273	$820.63	$820.65	$820.70