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	$200.71	8.863%	$218.4989	$218.50	$218.50	$218.50
Purchase #2	$94.88	12.676%	$106.907	$106.91	$106.90	$106.90
Purchase #3	$11.30	10.761%	$12.516	$12.52	$12.50	$12.50
Purchase #4	$93.73	6.697%	$100.0071	$100.01	$100.00	$100.00
Purchase #5	$108.41	6.334%	$115.2767	$115.28	$115.30	$115.30
Purchase #6	$117.61	6.168%	$124.8642	$124.86	$124.85	$124.90
Purchase #7	$195.29	11.874%	$218.4787	$218.48	$218.50	$218.50
7 purchase totals =	$821.93		$896.5486	$896.56	$896.55	$896.60