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	$127.72	4.189%	$133.0702	$133.07	$133.05	$133.10
Purchase #2	$238.78	13.550%	$271.1347	$271.13	$271.15	$271.10
Purchase #3	$37.26	9.652%	$40.8563	$40.86	$40.85	$40.90
Purchase #4	$5.54	7.290%	$5.9439	$5.94	$5.95	$5.90
Purchase #5	$196.56	4.806%	$206.0067	$206.01	$206.00	$206.00
Purchase #6	$25.86	9.611%	$28.3454	$28.35	$28.35	$28.30
Purchase #7	$63.82	13.329%	$72.3266	$72.33	$72.35	$72.30
7 purchase totals =	$695.54		$757.6838	$757.69	$757.70	$757.60