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	$115.56	9.705%	$126.7751	$126.78	$126.80	$126.80
Purchase #2	$30.47	9.438%	$33.3458	$33.35	$33.35	$33.30
Purchase #3	$94.63	11.870%	$105.8626	$105.86	$105.85	$105.90
Purchase #4	$157.79	7.368%	$169.416	$169.42	$169.40	$169.40
Purchase #5	$47.45	4.426%	$49.5501	$49.55	$49.55	$49.60
Purchase #6	$146.89	5.521%	$154.9998	$155.00	$155.00	$155.00
Purchase #7	$33.70	11.318%	$37.5142	$37.51	$37.50	$37.50
7 purchase totals =	$626.49		$677.4636	$677.47	$677.45	$677.50