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	$201.59	10.359%	$222.4727	$222.47	$222.45	$222.50
Purchase #2	$21.59	13.501%	$24.5049	$24.50	$24.50	$24.50
Purchase #3	$116.48	3.469%	$120.5207	$120.52	$120.50	$120.50
Purchase #4	$23.76	8.701%	$25.8274	$25.83	$25.85	$25.80
Purchase #5	$32.65	4.120%	$33.9952	$34.00	$34.00	$34.00
Purchase #6	$49.31	4.521%	$51.5393	$51.54	$51.55	$51.50
Purchase #7	$113.63	5.360%	$119.7206	$119.72	$119.70	$119.70
7 purchase totals =	$559.01		$598.5808	$598.58	$598.55	$598.50