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	$80.43	12.269%	$90.298	$90.30	$90.30	$90.30
Purchase #2	$74.62	8.219%	$80.753	$80.75	$80.75	$80.80
Purchase #3	$240.80	13.396%	$273.0576	$273.06	$273.05	$273.10
Purchase #4	$208.86	4.761%	$218.8038	$218.80	$218.80	$218.80
Purchase #5	$66.86	12.635%	$75.3078	$75.31	$75.30	$75.30
Purchase #6	$146.52	3.821%	$152.1185	$152.12	$152.10	$152.10
Purchase #7	$150.50	10.609%	$166.4665	$166.47	$166.45	$166.50
7 purchase totals =	$968.59		$1,056.8052	$1,056.81	$1,056.75	$1,056.90