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	$122.65	8.210%	$132.7196	$132.72	$132.70	$132.70
Purchase #2	$55.48	7.350%	$59.5578	$59.56	$59.55	$59.60
Purchase #3	$71.89	10.714%	$79.5923	$79.59	$79.60	$79.60
Purchase #4	$211.98	5.249%	$223.1068	$223.11	$223.10	$223.10
Purchase #5	$36.55	5.795%	$38.6681	$38.67	$38.65	$38.70
Purchase #6	$185.37	4.212%	$193.1778	$193.18	$193.20	$193.20
Purchase #7	$36.69	9.113%	$40.0336	$40.03	$40.05	$40.00
7 purchase totals =	$720.61		$766.8560	$766.86	$766.85	$766.90