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	$158.52	8.871%	$172.5823	$172.58	$172.60	$172.60
Purchase #2	$39.58	4.151%	$41.223	$41.22	$41.20	$41.20
Purchase #3	$35.51	3.577%	$36.7802	$36.78	$36.80	$36.80
Purchase #4	$222.71	12.295%	$250.0922	$250.09	$250.10	$250.10
Purchase #5	$203.72	6.374%	$216.7051	$216.71	$216.70	$216.70
Purchase #6	$246.52	4.196%	$256.864	$256.86	$256.85	$256.90
Purchase #7	$20.27	7.715%	$21.8338	$21.83	$21.85	$21.80
7 purchase totals =	$926.83		$996.0806	$996.07	$996.10	$996.10