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	$162.90	5.602%	$172.0257	$172.03	$172.05	$172.00
Purchase #2	$59.53	13.417%	$67.5171	$67.52	$67.50	$67.50
Purchase #3	$135.68	13.864%	$154.4907	$154.49	$154.50	$154.50
Purchase #4	$99.74	5.584%	$105.3095	$105.31	$105.30	$105.30
Purchase #5	$81.45	12.508%	$91.6378	$91.64	$91.65	$91.60
Purchase #6	$190.28	11.807%	$212.7464	$212.75	$212.75	$212.70
Purchase #7	$121.28	13.128%	$137.2016	$137.20	$137.20	$137.20
7 purchase totals =	$850.86		$940.9288	$940.94	$940.95	$940.80