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	$86.85	12.741%	$97.9156	$97.92	$97.90	$97.90
Purchase #2	$37.85	11.266%	$42.1142	$42.11	$42.10	$42.10
Purchase #3	$135.88	11.853%	$151.9859	$151.99	$152.00	$152.00
Purchase #4	$58.55	11.805%	$65.4618	$65.46	$65.45	$65.50
Purchase #5	$51.80	9.590%	$56.7676	$56.77	$56.75	$56.80
Purchase #6	$172.29	8.648%	$187.1896	$187.19	$187.20	$187.20
Purchase #7	$87.59	4.201%	$91.2697	$91.27	$91.25	$91.30
7 purchase totals =	$630.81		$692.7044	$692.71	$692.65	$692.80