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	$214.60	6.530%	$228.6134	$228.61	$228.60	$228.60
Purchase #2	$156.83	7.748%	$168.9812	$168.98	$169.00	$169.00
Purchase #3	$225.38	7.162%	$241.5217	$241.52	$241.50	$241.50
Purchase #4	$203.48	9.231%	$222.2632	$222.26	$222.25	$222.30
Purchase #5	$40.96	11.659%	$45.7355	$45.74	$45.75	$45.70
Purchase #6	$216.60	10.133%	$238.5481	$238.55	$238.55	$238.50
Purchase #7	$97.32	13.147%	$110.1147	$110.11	$110.10	$110.10
7 purchase totals =	$1,155.17		$1,255.7778	$1,255.77	$1,255.75	$1,255.70