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	$106.95	6.172%	$113.551	$113.55	$113.55	$113.60
Purchase #2	$64.54	3.548%	$66.8299	$66.83	$66.85	$66.80
Purchase #3	$114.76	12.154%	$128.7079	$128.71	$128.70	$128.70
Purchase #4	$13.73	12.679%	$15.4708	$15.47	$15.45	$15.50
Purchase #5	$40.67	4.707%	$42.5843	$42.58	$42.60	$42.60
Purchase #6	$102.75	7.461%	$110.4162	$110.42	$110.40	$110.40
Purchase #7	$68.53	6.239%	$72.8056	$72.81	$72.80	$72.80
7 purchase totals =	$511.93		$550.3657	$550.37	$550.35	$550.40