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	$88.61	3.541%	$91.7477	$91.75	$91.75	$91.70
Purchase #2	$136.41	3.105%	$140.6455	$140.65	$140.65	$140.60
Purchase #3	$76.33	11.543%	$85.1408	$85.14	$85.15	$85.10
Purchase #4	$139.61	4.110%	$145.348	$145.35	$145.35	$145.30
Purchase #5	$160.74	5.591%	$169.727	$169.73	$169.75	$169.70
Purchase #6	$185.90	5.492%	$196.1096	$196.11	$196.10	$196.10
Purchase #7	$13.96	7.602%	$15.0212	$15.02	$15.00	$15.00
7 purchase totals =	$801.56		$843.7398	$843.75	$843.75	$843.50