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	$141.54	12.250%	$158.8787	$158.88	$158.90	$158.90
Purchase #2	$138.49	3.602%	$143.4784	$143.48	$143.50	$143.50
Purchase #3	$221.38	12.576%	$249.2207	$249.22	$249.20	$249.20
Purchase #4	$141.94	6.429%	$151.0653	$151.07	$151.05	$151.10
Purchase #5	$29.59	10.591%	$32.7239	$32.72	$32.70	$32.70
Purchase #6	$210.93	10.383%	$232.8309	$232.83	$232.85	$232.80
Purchase #7	$59.89	3.749%	$62.1353	$62.14	$62.15	$62.10
7 purchase totals =	$943.76		$1,030.3332	$1,030.34	$1,030.35	$1,030.30