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	$103.98	8.378%	$112.6914	$112.69	$112.70	$112.70
Purchase #2	$217.39	5.345%	$229.0095	$229.01	$229.00	$229.00
Purchase #3	$64.29	5.285%	$67.6877	$67.69	$67.70	$67.70
Purchase #4	$198.60	10.434%	$219.3219	$219.32	$219.30	$219.30
Purchase #5	$6.37	12.155%	$7.1443	$7.14	$7.15	$7.10
Purchase #6	$230.83	7.151%	$247.3367	$247.34	$247.35	$247.30
Purchase #7	$63.81	13.327%	$72.314	$72.31	$72.30	$72.30
7 purchase totals =	$885.27		$955.5055	$955.50	$955.50	$955.40