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	$102.66	10.451%	$113.389	$113.39	$113.40	$113.40
Purchase #2	$245.85	12.250%	$275.9666	$275.97	$275.95	$276.00
Purchase #3	$228.60	8.754%	$248.6116	$248.61	$248.60	$248.60
Purchase #4	$201.48	8.459%	$218.5232	$218.52	$218.50	$218.50
Purchase #5	$140.93	7.810%	$151.9366	$151.94	$151.95	$151.90
Purchase #6	$161.51	3.331%	$166.8899	$166.89	$166.90	$166.90
Purchase #7	$240.49	4.208%	$250.6098	$250.61	$250.60	$250.60
7 purchase totals =	$1,321.52		$1,425.9267	$1,425.93	$1,425.90	$1,425.90