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	$35.53	5.724%	$37.5637	$37.56	$37.55	$37.60
Purchase #2	$44.36	3.655%	$45.9814	$45.98	$46.00	$46.00
Purchase #3	$198.26	10.801%	$219.6741	$219.67	$219.65	$219.70
Purchase #4	$63.89	8.712%	$69.4561	$69.46	$69.45	$69.50
Purchase #5	$208.59	4.315%	$217.5907	$217.59	$217.60	$217.60
Purchase #6	$138.37	6.839%	$147.8331	$147.83	$147.85	$147.80
Purchase #7	$61.45	3.869%	$63.8275	$63.83	$63.85	$63.80
7 purchase totals =	$750.45		$801.9266	$801.92	$801.95	$802.00