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	$32.42	8.766%	$35.2619	$35.26	$35.25	$35.30
Purchase #2	$103.31	12.749%	$116.481	$116.48	$116.50	$116.50
Purchase #3	$74.96	11.384%	$83.4934	$83.49	$83.50	$83.50
Purchase #4	$125.84	11.834%	$140.7319	$140.73	$140.75	$140.70
Purchase #5	$17.89	13.322%	$20.2733	$20.27	$20.25	$20.30
Purchase #6	$180.73	6.583%	$192.6275	$192.63	$192.65	$192.60
Purchase #7	$71.44	4.873%	$74.9213	$74.92	$74.90	$74.90
7 purchase totals =	$606.59		$663.7903	$663.78	$663.80	$663.80