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	$187.51	11.604%	$209.2687	$209.27	$209.25	$209.30
Purchase #2	$196.25	8.159%	$212.262	$212.26	$212.25	$212.30
Purchase #3	$78.70	10.106%	$86.6534	$86.65	$86.65	$86.70
Purchase #4	$230.77	3.387%	$238.5862	$238.59	$238.60	$238.60
Purchase #5	$80.36	9.694%	$88.1501	$88.15	$88.15	$88.20
Purchase #6	$83.70	8.234%	$90.5919	$90.59	$90.60	$90.60
Purchase #7	$7.94	11.452%	$8.8493	$8.85	$8.85	$8.80
7 purchase totals =	$865.23		$934.3616	$934.36	$934.35	$934.50