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	$217.74	6.849%	$232.653	$232.65	$232.65	$232.70
Purchase #2	$81.87	9.263%	$89.4536	$89.45	$89.45	$89.50
Purchase #3	$204.63	9.256%	$223.5706	$223.57	$223.55	$223.60
Purchase #4	$185.40	7.242%	$198.8267	$198.83	$198.85	$198.80
Purchase #5	$119.46	3.614%	$123.7773	$123.78	$123.80	$123.80
Purchase #6	$135.42	8.616%	$147.0878	$147.09	$147.10	$147.10
Purchase #7	$63.65	12.797%	$71.7953	$71.80	$71.80	$71.80
7 purchase totals =	$1,008.17		$1,087.1643	$1,087.17	$1,087.20	$1,087.30