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	$36.91	9.118%	$40.2755	$40.28	$40.30	$40.30
Purchase #2	$12.72	13.857%	$14.4826	$14.48	$14.50	$14.50
Purchase #3	$13.82	13.347%	$15.6646	$15.66	$15.65	$15.70
Purchase #4	$37.72	5.801%	$39.9081	$39.91	$39.90	$39.90
Purchase #5	$151.36	8.396%	$164.0682	$164.07	$164.05	$164.10
Purchase #6	$21.33	7.513%	$22.9325	$22.93	$22.95	$22.90
Purchase #7	$160.55	4.308%	$167.4665	$167.47	$167.45	$167.50
7 purchase totals =	$434.41		$464.7980	$464.80	$464.80	$464.90