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	$100.38	11.250%	$111.6728	$111.67	$111.65	$111.70
Purchase #2	$118.71	11.699%	$132.5979	$132.60	$132.60	$132.60
Purchase #3	$23.47	9.289%	$25.6501	$25.65	$25.65	$25.70
Purchase #4	$211.50	6.650%	$225.5648	$225.56	$225.55	$225.60
Purchase #5	$197.52	7.402%	$212.1404	$212.14	$212.15	$212.10
Purchase #6	$63.81	7.530%	$68.6149	$68.61	$68.60	$68.60
Purchase #7	$119.89	6.578%	$127.7764	$127.78	$127.80	$127.80
7 purchase totals =	$835.28		$904.0173	$904.01	$904.00	$904.10