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	$205.55	7.846%	$221.6775	$221.68	$221.70	$221.70
Purchase #2	$31.53	8.310%	$34.1501	$34.15	$34.15	$34.20
Purchase #3	$156.76	7.630%	$168.7208	$168.72	$168.70	$168.70
Purchase #4	$228.31	6.262%	$242.6068	$242.61	$242.60	$242.60
Purchase #5	$140.87	10.823%	$156.1164	$156.12	$156.10	$156.10
Purchase #6	$72.77	7.441%	$78.1848	$78.18	$78.20	$78.20
Purchase #7	$205.84	8.585%	$223.5114	$223.51	$223.50	$223.50
7 purchase totals =	$1,041.63		$1,124.9678	$1,124.97	$1,124.95	$1,125.00