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	$10.64	3.638%	$11.0271	$11.03	$11.05	$11.00
Purchase #2	$208.76	11.290%	$232.329	$232.33	$232.35	$232.30
Purchase #3	$242.74	6.657%	$258.8992	$258.90	$258.90	$258.90
Purchase #4	$20.56	5.867%	$21.7663	$21.77	$21.75	$21.80
Purchase #5	$72.72	8.594%	$78.9696	$78.97	$78.95	$79.00
Purchase #6	$68.84	5.695%	$72.7604	$72.76	$72.75	$72.80
Purchase #7	$53.41	11.249%	$59.4181	$59.42	$59.40	$59.40
7 purchase totals =	$677.67		$735.1697	$735.18	$735.15	$735.20