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	$208.61	6.185%	$221.5125	$221.51	$221.50	$221.50
Purchase #2	$19.31	4.388%	$20.1573	$20.16	$20.15	$20.20
Purchase #3	$136.88	5.793%	$144.8095	$144.81	$144.80	$144.80
Purchase #4	$231.52	4.359%	$241.612	$241.61	$241.60	$241.60
Purchase #5	$84.46	11.319%	$94.02	$94.02	$94.00	$94.00
Purchase #6	$152.54	4.493%	$159.3936	$159.39	$159.40	$159.40
Purchase #7	$36.77	12.562%	$41.389	$41.39	$41.40	$41.40
7 purchase totals =	$870.09		$922.8939	$922.89	$922.85	$922.90