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	$41.57	5.806%	$43.9836	$43.98	$44.00	$44.00
Purchase #2	$172.67	3.816%	$179.2591	$179.26	$179.25	$179.30
Purchase #3	$56.69	4.506%	$59.2445	$59.24	$59.25	$59.20
Purchase #4	$44.83	3.692%	$46.4851	$46.49	$46.50	$46.50
Purchase #5	$26.28	13.725%	$29.8869	$29.89	$29.90	$29.90
Purchase #6	$52.57	11.813%	$58.7801	$58.78	$58.80	$58.80
Purchase #7	$237.58	3.871%	$246.7767	$246.78	$246.80	$246.80
7 purchase totals =	$632.19		$664.4160	$664.42	$664.50	$664.50