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	$169.51	13.512%	$192.4142	$192.41	$192.40	$192.40
Purchase #2	$211.93	11.493%	$236.2871	$236.29	$236.30	$236.30
Purchase #3	$109.42	10.717%	$121.1465	$121.15	$121.15	$121.10
Purchase #4	$139.62	7.761%	$150.4559	$150.46	$150.45	$150.50
Purchase #5	$38.41	13.531%	$43.6073	$43.61	$43.60	$43.60
Purchase #6	$229.85	9.458%	$251.5892	$251.59	$251.60	$251.60
Purchase #7	$7.29	8.398%	$7.9022	$7.90	$7.90	$7.90
7 purchase totals =	$906.03		$1,003.4024	$1,003.41	$1,003.40	$1,003.40