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	$105.93	3.679%	$109.8272	$109.83	$109.85	$109.80
Purchase #2	$66.79	12.321%	$75.0192	$75.02	$75.00	$75.00
Purchase #3	$11.52	12.842%	$12.9994	$13.00	$13.00	$13.00
Purchase #4	$63.52	11.583%	$70.8775	$70.88	$70.90	$70.90
Purchase #5	$20.87	6.744%	$22.2775	$22.28	$22.30	$22.30
Purchase #6	$11.40	9.393%	$12.4708	$12.47	$12.45	$12.50
Purchase #7	$86.89	4.130%	$90.4786	$90.48	$90.50	$90.50
7 purchase totals =	$366.92		$393.9502	$393.96	$394.00	$394.00