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	$40.69	10.807%	$45.0874	$45.09	$45.10	$45.10
Purchase #2	$33.63	11.538%	$37.5102	$37.51	$37.50	$37.50
Purchase #3	$202.48	12.348%	$227.4822	$227.48	$227.50	$227.50
Purchase #4	$146.64	8.298%	$158.8082	$158.81	$158.80	$158.80
Purchase #5	$72.42	13.276%	$82.0345	$82.03	$82.05	$82.00
Purchase #6	$142.53	5.630%	$150.5544	$150.55	$150.55	$150.60
Purchase #7	$105.84	9.520%	$115.916	$115.92	$115.90	$115.90
7 purchase totals =	$744.23		$817.3929	$817.39	$817.40	$817.40