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	$117.50	11.389%	$130.8821	$130.88	$130.90	$130.90
Purchase #2	$154.59	3.368%	$159.7966	$159.80	$159.80	$159.80
Purchase #3	$213.37	9.503%	$233.6466	$233.65	$233.65	$233.60
Purchase #4	$77.29	8.606%	$83.9416	$83.94	$83.95	$83.90
Purchase #5	$94.57	9.869%	$103.9031	$103.90	$103.90	$103.90
Purchase #6	$172.70	10.276%	$190.4467	$190.45	$190.45	$190.40
Purchase #7	$100.88	12.381%	$113.37	$113.37	$113.35	$113.40
7 purchase totals =	$930.90		$1,015.9867	$1,015.99	$1,016.00	$1,015.90