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	$167.73	13.836%	$190.9371	$190.94	$190.95	$190.90
Purchase #2	$229.40	13.215%	$259.7152	$259.72	$259.70	$259.70
Purchase #3	$217.67	6.480%	$231.775	$231.78	$231.80	$231.80
Purchase #4	$33.26	5.327%	$35.0318	$35.03	$35.05	$35.00
Purchase #5	$116.52	5.162%	$122.5348	$122.53	$122.55	$122.50
Purchase #6	$43.46	7.724%	$46.8169	$46.82	$46.80	$46.80
Purchase #7	$191.57	4.148%	$199.5163	$199.52	$199.50	$199.50
7 purchase totals =	$999.61		$1,086.3271	$1,086.34	$1,086.35	$1,086.20