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	$217.57	7.523%	$233.9378	$233.94	$233.95	$233.90
Purchase #2	$102.29	3.331%	$105.6973	$105.70	$105.70	$105.70
Purchase #3	$87.67	5.635%	$92.6102	$92.61	$92.60	$92.60
Purchase #4	$113.47	7.815%	$122.3377	$122.34	$122.35	$122.30
Purchase #5	$29.90	5.556%	$31.5612	$31.56	$31.55	$31.60
Purchase #6	$145.26	4.426%	$151.6892	$151.69	$151.70	$151.70
Purchase #7	$59.77	3.127%	$61.639	$61.64	$61.65	$61.60
7 purchase totals =	$755.93		$799.4724	$799.48	$799.50	$799.40