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	$119.93	6.297%	$127.482	$127.48	$127.50	$127.50
Purchase #2	$237.90	10.199%	$262.1634	$262.16	$262.15	$262.20
Purchase #3	$12.63	8.185%	$13.6638	$13.66	$13.65	$13.70
Purchase #4	$186.92	12.730%	$210.7149	$210.71	$210.70	$210.70
Purchase #5	$93.70	13.492%	$106.342	$106.34	$106.35	$106.30
Purchase #6	$54.96	8.398%	$59.5755	$59.58	$59.60	$59.60
Purchase #7	$131.49	11.316%	$146.3694	$146.37	$146.35	$146.40
7 purchase totals =	$837.53		$926.3110	$926.30	$926.30	$926.40