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	$230.52	6.244%	$244.9137	$244.91	$244.90	$244.90
Purchase #2	$89.60	12.161%	$100.4963	$100.50	$100.50	$100.50
Purchase #3	$81.28	6.386%	$86.4705	$86.47	$86.45	$86.50
Purchase #4	$125.49	9.562%	$137.4894	$137.49	$137.50	$137.50
Purchase #5	$216.82	11.602%	$241.9755	$241.98	$242.00	$242.00
Purchase #6	$39.90	5.498%	$42.0937	$42.09	$42.10	$42.10
Purchase #7	$217.25	12.703%	$244.8473	$244.85	$244.85	$244.80
7 purchase totals =	$1,000.86		$1,098.2864	$1,098.29	$1,098.30	$1,098.30