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	$11.28	3.473%	$11.6718	$11.67	$11.65	$11.70
Purchase #2	$18.57	10.153%	$20.4554	$20.46	$20.45	$20.50
Purchase #3	$49.39	10.618%	$54.6342	$54.63	$54.65	$54.60
Purchase #4	$31.87	6.845%	$34.0515	$34.05	$34.05	$34.10
Purchase #5	$245.87	12.105%	$275.6326	$275.63	$275.65	$275.60
Purchase #6	$38.94	9.375%	$42.5906	$42.59	$42.60	$42.60
Purchase #7	$159.27	6.123%	$169.0221	$169.02	$169.00	$169.00
7 purchase totals =	$555.19		$608.0582	$608.05	$608.05	$608.10