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	$56.53	9.437%	$61.8647	$61.86	$61.85	$61.90
Purchase #2	$34.43	12.129%	$38.606	$38.61	$38.60	$38.60
Purchase #3	$54.67	7.465%	$58.7511	$58.75	$58.75	$58.80
Purchase #4	$40.92	6.248%	$43.4767	$43.48	$43.50	$43.50
Purchase #5	$146.61	3.606%	$151.8968	$151.90	$151.90	$151.90
Purchase #6	$197.72	6.627%	$210.8229	$210.82	$210.80	$210.80
Purchase #7	$161.67	13.276%	$183.1333	$183.13	$183.15	$183.10
7 purchase totals =	$692.55		$748.5515	$748.55	$748.55	$748.60