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	$207.65	7.467%	$223.1552	$223.16	$223.15	$223.20
Purchase #2	$94.58	3.631%	$98.0142	$98.01	$98.00	$98.00
Purchase #3	$250.71	6.294%	$266.4897	$266.49	$266.50	$266.50
Purchase #4	$180.26	5.644%	$190.4339	$190.43	$190.45	$190.40
Purchase #5	$126.45	5.130%	$132.9369	$132.94	$132.95	$132.90
Purchase #6	$29.65	12.763%	$33.4342	$33.43	$33.45	$33.40
Purchase #7	$208.55	6.872%	$222.8816	$222.88	$222.90	$222.90
7 purchase totals =	$1,097.85		$1,167.3457	$1,167.34	$1,167.40	$1,167.30