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	$55.44	13.593%	$62.976	$62.98	$63.00	$63.00
Purchase #2	$199.40	9.544%	$218.4307	$218.43	$218.45	$218.40
Purchase #3	$115.83	13.561%	$131.5377	$131.54	$131.55	$131.50
Purchase #4	$11.52	3.460%	$11.9186	$11.92	$11.90	$11.90
Purchase #5	$124.74	5.257%	$131.2976	$131.30	$131.30	$131.30
Purchase #6	$14.95	3.804%	$15.5187	$15.52	$15.50	$15.50
Purchase #7	$26.40	4.313%	$27.5386	$27.54	$27.55	$27.50
7 purchase totals =	$548.28		$599.2179	$599.23	$599.25	$599.10