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	$110.87	5.738%	$117.2317	$117.23	$117.25	$117.20
Purchase #2	$150.46	4.700%	$157.5316	$157.53	$157.55	$157.50
Purchase #3	$20.91	5.714%	$22.1048	$22.10	$22.10	$22.10
Purchase #4	$180.99	8.383%	$196.1624	$196.16	$196.15	$196.20
Purchase #5	$29.42	10.296%	$32.4491	$32.45	$32.45	$32.40
Purchase #6	$233.85	9.163%	$255.2777	$255.28	$255.30	$255.30
Purchase #7	$41.31	9.309%	$45.1555	$45.16	$45.15	$45.20
7 purchase totals =	$767.81		$825.9128	$825.91	$825.95	$825.90