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	$102.48	11.186%	$113.9434	$113.94	$113.95	$113.90
Purchase #2	$227.31	13.455%	$257.8946	$257.89	$257.90	$257.90
Purchase #3	$71.43	6.273%	$75.9108	$75.91	$75.90	$75.90
Purchase #4	$64.52	11.388%	$71.8675	$71.87	$71.85	$71.90
Purchase #5	$133.68	6.661%	$142.5844	$142.58	$142.60	$142.60
Purchase #6	$38.62	12.456%	$43.4305	$43.43	$43.45	$43.40
Purchase #7	$185.54	3.774%	$192.5423	$192.54	$192.55	$192.50
7 purchase totals =	$823.58		$898.1735	$898.16	$898.20	$898.10