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	$105.67	10.873%	$117.1595	$117.16	$117.15	$117.20
Purchase #2	$213.33	4.281%	$222.4627	$222.46	$222.45	$222.50
Purchase #3	$209.81	7.630%	$225.8185	$225.82	$225.80	$225.80
Purchase #4	$175.65	7.532%	$188.88	$188.88	$188.90	$188.90
Purchase #5	$105.39	12.535%	$118.6006	$118.60	$118.60	$118.60
Purchase #6	$233.51	11.385%	$260.0951	$260.10	$260.10	$260.10
Purchase #7	$138.47	13.605%	$157.3088	$157.31	$157.30	$157.30
7 purchase totals =	$1,181.83		$1,290.3252	$1,290.33	$1,290.30	$1,290.40