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	$172.91	11.261%	$192.3814	$192.38	$192.40	$192.40
Purchase #2	$157.41	9.328%	$172.0932	$172.09	$172.10	$172.10
Purchase #3	$107.83	9.437%	$118.0059	$118.01	$118.00	$118.00
Purchase #4	$72.94	8.667%	$79.2617	$79.26	$79.25	$79.30
Purchase #5	$71.27	9.621%	$78.1269	$78.13	$78.15	$78.10
Purchase #6	$26.30	13.654%	$29.891	$29.89	$29.90	$29.90
Purchase #7	$58.90	13.807%	$67.0323	$67.03	$67.05	$67.00
7 purchase totals =	$667.56		$736.7924	$736.79	$736.85	$736.80