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	$83.67	8.675%	$90.9284	$90.93	$90.95	$90.90
Purchase #2	$191.51	7.780%	$206.4095	$206.41	$206.40	$206.40
Purchase #3	$41.39	11.526%	$46.1606	$46.16	$46.15	$46.20
Purchase #4	$197.52	12.842%	$222.8855	$222.89	$222.90	$222.90
Purchase #5	$154.38	5.610%	$163.0407	$163.04	$163.05	$163.00
Purchase #6	$154.81	3.397%	$160.0689	$160.07	$160.05	$160.10
Purchase #7	$172.48	9.468%	$188.8104	$188.81	$188.80	$188.80
7 purchase totals =	$995.76		$1,078.3040	$1,078.31	$1,078.30	$1,078.30