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	$102.51	9.107%	$111.8456	$111.85	$111.85	$111.80
Purchase #2	$30.52	8.234%	$33.033	$33.03	$33.05	$33.00
Purchase #3	$138.30	5.806%	$146.3297	$146.33	$146.35	$146.30
Purchase #4	$139.40	9.724%	$152.9553	$152.96	$152.95	$153.00
Purchase #5	$123.33	7.454%	$132.523	$132.52	$132.50	$132.50
Purchase #6	$114.61	8.561%	$124.4218	$124.42	$124.40	$124.40
Purchase #7	$22.72	8.868%	$24.7348	$24.73	$24.75	$24.70
7 purchase totals =	$671.39		$725.8432	$725.84	$725.85	$725.70