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	$72.51	6.557%	$77.2645	$77.26	$77.25	$77.30
Purchase #2	$223.52	6.749%	$238.6054	$238.61	$238.60	$238.60
Purchase #3	$139.87	4.680%	$146.4159	$146.42	$146.40	$146.40
Purchase #4	$115.96	4.452%	$121.1225	$121.12	$121.10	$121.10
Purchase #5	$46.55	10.870%	$51.61	$51.61	$51.60	$51.60
Purchase #6	$41.61	8.291%	$45.0599	$45.06	$45.05	$45.10
Purchase #7	$20.64	6.212%	$21.9222	$21.92	$21.90	$21.90
7 purchase totals =	$660.66		$702.0004	$702.00	$701.90	$702.00