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	$104.77	8.664%	$113.8473	$113.85	$113.85	$113.80
Purchase #2	$66.87	4.518%	$69.8912	$69.89	$69.90	$69.90
Purchase #3	$5.78	12.576%	$6.5069	$6.51	$6.50	$6.50
Purchase #4	$180.42	7.837%	$194.5595	$194.56	$194.55	$194.60
Purchase #5	$64.49	3.181%	$66.5414	$66.54	$66.55	$66.50
Purchase #6	$172.32	4.287%	$179.7074	$179.71	$179.70	$179.70
Purchase #7	$18.77	9.809%	$20.6111	$20.61	$20.60	$20.60
7 purchase totals =	$613.42		$651.6648	$651.67	$651.65	$651.60