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	$59.28	12.635%	$66.77	$66.77	$66.75	$66.80
Purchase #2	$32.99	8.815%	$35.8981	$35.90	$35.90	$35.90
Purchase #3	$167.83	11.390%	$186.9458	$186.95	$186.95	$186.90
Purchase #4	$192.50	10.398%	$212.5162	$212.52	$212.50	$212.50
Purchase #5	$101.57	3.747%	$105.3758	$105.38	$105.40	$105.40
Purchase #6	$215.76	8.413%	$233.9119	$233.91	$233.90	$233.90
Purchase #7	$5.26	4.189%	$5.4803	$5.48	$5.50	$5.50
7 purchase totals =	$775.19		$846.8981	$846.91	$846.90	$846.90