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	$222.35	8.564%	$241.3921	$241.39	$241.40	$241.40
Purchase #2	$203.88	10.612%	$225.5157	$225.52	$225.50	$225.50
Purchase #3	$170.63	12.746%	$192.3785	$192.38	$192.40	$192.40
Purchase #4	$184.70	6.505%	$196.7147	$196.71	$196.70	$196.70
Purchase #5	$37.83	11.333%	$42.1173	$42.12	$42.10	$42.10
Purchase #6	$73.26	12.261%	$82.2424	$82.24	$82.25	$82.20
Purchase #7	$218.25	6.141%	$231.6527	$231.65	$231.65	$231.70
7 purchase totals =	$1,110.90		$1,212.0134	$1,212.01	$1,212.00	$1,212.00