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	$105.92	3.468%	$109.5933	$109.59	$109.60	$109.60
Purchase #2	$12.69	9.246%	$13.8633	$13.86	$13.85	$13.90
Purchase #3	$36.93	11.123%	$41.0377	$41.04	$41.05	$41.00
Purchase #4	$77.40	7.569%	$83.2584	$83.26	$83.25	$83.30
Purchase #5	$36.46	3.104%	$37.5917	$37.59	$37.60	$37.60
Purchase #6	$165.50	7.317%	$177.6096	$177.61	$177.60	$177.60
Purchase #7	$136.77	9.282%	$149.465	$149.47	$149.45	$149.50
7 purchase totals =	$571.67		$612.4190	$612.42	$612.40	$612.50