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	$237.46	8.155%	$256.8249	$256.82	$256.80	$256.80
Purchase #2	$76.90	9.384%	$84.1163	$84.12	$84.10	$84.10
Purchase #3	$185.47	8.224%	$200.7231	$200.72	$200.70	$200.70
Purchase #4	$85.95	5.198%	$90.4177	$90.42	$90.40	$90.40
Purchase #5	$107.80	7.791%	$116.1987	$116.20	$116.20	$116.20
Purchase #6	$235.27	8.156%	$254.4586	$254.46	$254.45	$254.50
Purchase #7	$44.86	13.306%	$50.8291	$50.83	$50.85	$50.80
7 purchase totals =	$973.71		$1,053.5684	$1,053.57	$1,053.50	$1,053.50