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	$151.93	3.222%	$156.8252	$156.83	$156.85	$156.80
Purchase #2	$32.90	4.859%	$34.4986	$34.50	$34.50	$34.50
Purchase #3	$55.84	10.868%	$61.9087	$61.91	$61.90	$61.90
Purchase #4	$56.83	7.345%	$61.0042	$61.00	$61.00	$61.00
Purchase #5	$68.89	10.859%	$76.3708	$76.37	$76.35	$76.40
Purchase #6	$82.48	12.839%	$93.0696	$93.07	$93.05	$93.10
Purchase #7	$116.84	3.419%	$120.8348	$120.83	$120.85	$120.80
7 purchase totals =	$565.71		$604.5119	$604.51	$604.50	$604.50