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	$17.94	8.525%	$19.4694	$19.47	$19.45	$19.50
Purchase #2	$208.46	3.695%	$216.1626	$216.16	$216.15	$216.20
Purchase #3	$35.79	12.853%	$40.3901	$40.39	$40.40	$40.40
Purchase #4	$87.37	5.824%	$92.4584	$92.46	$92.45	$92.50
Purchase #5	$88.39	4.420%	$92.2968	$92.30	$92.30	$92.30
Purchase #6	$180.71	8.490%	$196.0523	$196.05	$196.05	$196.10
Purchase #7	$121.54	12.756%	$137.0436	$137.04	$137.05	$137.00
7 purchase totals =	$740.20		$793.8732	$793.87	$793.85	$794.00