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	$33.50	4.610%	$35.0444	$35.04	$35.05	$35.00
Purchase #2	$65.83	9.649%	$72.1819	$72.18	$72.20	$72.20
Purchase #3	$43.45	13.510%	$49.3201	$49.32	$49.30	$49.30
Purchase #4	$150.77	6.856%	$161.1068	$161.11	$161.10	$161.10
Purchase #5	$125.77	4.678%	$131.6535	$131.65	$131.65	$131.70
Purchase #6	$136.33	10.687%	$150.8996	$150.90	$150.90	$150.90
Purchase #7	$14.37	5.468%	$15.1558	$15.16	$15.15	$15.20
7 purchase totals =	$570.02		$615.3621	$615.36	$615.35	$615.40