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	$210.76	6.246%	$223.9241	$223.92	$223.90	$223.90
Purchase #2	$93.82	7.217%	$100.591	$100.59	$100.60	$100.60
Purchase #3	$131.48	7.632%	$141.5146	$141.51	$141.50	$141.50
Purchase #4	$29.34	5.468%	$30.9443	$30.94	$30.95	$30.90
Purchase #5	$132.82	4.821%	$139.2233	$139.22	$139.20	$139.20
Purchase #6	$197.50	4.853%	$207.0847	$207.08	$207.10	$207.10
Purchase #7	$55.74	11.525%	$62.164	$62.16	$62.15	$62.20
7 purchase totals =	$851.46		$905.4460	$905.42	$905.40	$905.40