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	$34.58	8.293%	$37.4477	$37.45	$37.45	$37.40
Purchase #2	$238.31	7.864%	$257.0507	$257.05	$257.05	$257.10
Purchase #3	$138.75	7.770%	$149.5309	$149.53	$149.55	$149.50
Purchase #4	$201.29	13.684%	$228.8345	$228.83	$228.85	$228.80
Purchase #5	$28.39	12.325%	$31.8891	$31.89	$31.90	$31.90
Purchase #6	$219.50	6.394%	$233.5348	$233.53	$233.55	$233.50
Purchase #7	$75.27	13.501%	$85.4322	$85.43	$85.45	$85.40
7 purchase totals =	$936.09		$1,023.7199	$1,023.71	$1,023.80	$1,023.60