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	$32.83	3.126%	$33.8563	$33.86	$33.85	$33.90
Purchase #2	$18.81	11.277%	$20.9312	$20.93	$20.95	$20.90
Purchase #3	$62.50	13.509%	$70.9431	$70.94	$70.95	$70.90
Purchase #4	$223.80	12.578%	$251.9496	$251.95	$251.95	$251.90
Purchase #5	$152.89	11.380%	$170.2889	$170.29	$170.30	$170.30
Purchase #6	$144.69	4.753%	$151.5671	$151.57	$151.55	$151.60
Purchase #7	$185.27	4.380%	$193.3848	$193.38	$193.40	$193.40
7 purchase totals =	$820.79		$892.9210	$892.92	$892.95	$892.90