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	$88.92	4.105%	$92.5702	$92.57	$92.55	$92.60
Purchase #2	$47.79	9.687%	$52.4194	$52.42	$52.40	$52.40
Purchase #3	$231.61	10.251%	$255.3523	$255.35	$255.35	$255.40
Purchase #4	$86.48	10.244%	$95.339	$95.34	$95.35	$95.30
Purchase #5	$30.72	9.844%	$33.7441	$33.74	$33.75	$33.70
Purchase #6	$93.33	3.140%	$96.2606	$96.26	$96.25	$96.30
Purchase #7	$248.36	8.657%	$269.8605	$269.86	$269.85	$269.90
7 purchase totals =	$827.21		$895.5461	$895.54	$895.50	$895.60