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	$60.25	9.580%	$66.022	$66.02	$66.00	$66.00
Purchase #2	$73.91	6.167%	$78.468	$78.47	$78.45	$78.50
Purchase #3	$66.29	5.333%	$69.8252	$69.83	$69.85	$69.80
Purchase #4	$200.47	12.191%	$224.9093	$224.91	$224.90	$224.90
Purchase #5	$141.33	11.770%	$157.9645	$157.96	$157.95	$158.00
Purchase #6	$75.86	9.500%	$83.0667	$83.07	$83.05	$83.10
Purchase #7	$57.69	5.668%	$60.9599	$60.96	$60.95	$61.00
7 purchase totals =	$675.80		$741.2156	$741.22	$741.15	$741.30