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	$225.77	9.766%	$247.8187	$247.82	$247.80	$247.80
Purchase #2	$118.79	12.246%	$133.337	$133.34	$133.35	$133.30
Purchase #3	$91.98	11.389%	$102.4556	$102.46	$102.45	$102.50
Purchase #4	$78.60	3.630%	$81.4532	$81.45	$81.45	$81.50
Purchase #5	$149.43	13.450%	$169.5283	$169.53	$169.55	$169.50
Purchase #6	$145.43	5.150%	$152.9196	$152.92	$152.90	$152.90
Purchase #7	$118.56	7.305%	$127.2208	$127.22	$127.20	$127.20
7 purchase totals =	$928.56		$1,014.7332	$1,014.74	$1,014.70	$1,014.70