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	$194.77	6.799%	$208.0124	$208.01	$208.00	$208.00
Purchase #2	$71.85	3.839%	$74.6083	$74.61	$74.60	$74.60
Purchase #3	$36.77	11.174%	$40.8787	$40.88	$40.90	$40.90
Purchase #4	$29.45	12.171%	$33.0344	$33.03	$33.05	$33.00
Purchase #5	$63.72	4.331%	$66.4797	$66.48	$66.50	$66.50
Purchase #6	$26.61	3.547%	$27.5539	$27.55	$27.55	$27.60
Purchase #7	$114.94	13.659%	$130.6397	$130.64	$130.65	$130.60
7 purchase totals =	$538.11		$581.2071	$581.20	$581.25	$581.20