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	$206.58	5.490%	$217.9212	$217.92	$217.90	$217.90
Purchase #2	$63.72	11.819%	$71.2511	$71.25	$71.25	$71.30
Purchase #3	$57.69	13.749%	$65.6218	$65.62	$65.60	$65.60
Purchase #4	$158.46	8.777%	$172.368	$172.37	$172.35	$172.40
Purchase #5	$68.71	9.428%	$75.188	$75.19	$75.20	$75.20
Purchase #6	$162.30	8.776%	$176.5434	$176.54	$176.55	$176.50
Purchase #7	$50.76	11.427%	$56.5603	$56.56	$56.55	$56.60
7 purchase totals =	$768.22		$835.4538	$835.45	$835.40	$835.50