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	$216.26	13.541%	$245.5438	$245.54	$245.55	$245.50
Purchase #2	$50.25	9.547%	$55.0474	$55.05	$55.05	$55.00
Purchase #3	$157.91	8.577%	$171.4539	$171.45	$171.45	$171.50
Purchase #4	$116.84	3.738%	$121.2075	$121.21	$121.20	$121.20
Purchase #5	$95.96	3.338%	$99.1631	$99.16	$99.15	$99.20
Purchase #6	$245.95	5.215%	$258.7763	$258.78	$258.80	$258.80
Purchase #7	$25.59	6.439%	$27.2377	$27.24	$27.25	$27.20
7 purchase totals =	$908.76		$978.4297	$978.43	$978.45	$978.40