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	$204.52	9.150%	$223.2336	$223.23	$223.25	$223.20
Purchase #2	$15.44	3.854%	$16.0351	$16.04	$16.05	$16.00
Purchase #3	$184.32	6.181%	$195.7128	$195.71	$195.70	$195.70
Purchase #4	$179.59	9.424%	$196.5146	$196.51	$196.50	$196.50
Purchase #5	$145.88	8.700%	$158.5716	$158.57	$158.55	$158.60
Purchase #6	$88.57	8.139%	$95.7787	$95.78	$95.80	$95.80
Purchase #7	$64.28	3.604%	$66.5967	$66.60	$66.60	$66.60
7 purchase totals =	$882.60		$952.4431	$952.44	$952.45	$952.40