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	$193.52	10.377%	$213.6016	$213.60	$213.60	$213.60
Purchase #2	$63.51	6.773%	$67.8115	$67.81	$67.80	$67.80
Purchase #3	$37.94	5.769%	$40.1288	$40.13	$40.15	$40.10
Purchase #4	$148.60	8.232%	$160.8328	$160.83	$160.85	$160.80
Purchase #5	$230.27	6.380%	$244.9612	$244.96	$244.95	$245.00
Purchase #6	$117.40	11.506%	$130.908	$130.91	$130.90	$130.90
Purchase #7	$92.64	13.448%	$105.0982	$105.10	$105.10	$105.10
7 purchase totals =	$883.88		$963.3421	$963.34	$963.35	$963.30