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	$37.75	7.680%	$40.6492	$40.65	$40.65	$40.60
Purchase #2	$99.37	11.825%	$111.1205	$111.12	$111.10	$111.10
Purchase #3	$232.39	13.124%	$262.8889	$262.89	$262.90	$262.90
Purchase #4	$60.88	6.218%	$64.6655	$64.67	$64.65	$64.70
Purchase #5	$11.62	12.235%	$13.0417	$13.04	$13.05	$13.00
Purchase #6	$58.53	9.548%	$64.1184	$64.12	$64.10	$64.10
Purchase #7	$87.40	7.421%	$93.886	$93.89	$93.90	$93.90
7 purchase totals =	$587.94		$650.3702	$650.38	$650.35	$650.30