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	$157.39	10.344%	$173.6704	$173.67	$173.65	$173.70
Purchase #2	$64.93	12.182%	$72.8398	$72.84	$72.85	$72.80
Purchase #3	$167.84	10.751%	$185.8845	$185.88	$185.90	$185.90
Purchase #4	$37.78	11.191%	$42.008	$42.01	$42.00	$42.00
Purchase #5	$240.62	8.682%	$261.5106	$261.51	$261.50	$261.50
Purchase #6	$158.83	3.509%	$164.4033	$164.40	$164.40	$164.40
Purchase #7	$109.48	13.361%	$124.1076	$124.11	$124.10	$124.10
7 purchase totals =	$936.87		$1,024.4242	$1,024.42	$1,024.40	$1,024.40