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	$10.63	8.658%	$11.5503	$11.55	$11.55	$11.60
Purchase #2	$31.96	12.544%	$35.9691	$35.97	$35.95	$36.00
Purchase #3	$105.61	13.272%	$119.6266	$119.63	$119.65	$119.60
Purchase #4	$119.47	6.795%	$127.588	$127.59	$127.60	$127.60
Purchase #5	$134.41	4.541%	$140.5136	$140.51	$140.50	$140.50
Purchase #6	$98.86	13.303%	$112.0113	$112.01	$112.00	$112.00
Purchase #7	$104.43	12.853%	$117.8524	$117.85	$117.85	$117.90
7 purchase totals =	$605.37		$665.1113	$665.11	$665.10	$665.20