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	$132.57	9.669%	$145.3882	$145.39	$145.40	$145.40
Purchase #2	$242.73	4.443%	$253.5145	$253.51	$253.50	$253.50
Purchase #3	$210.68	11.343%	$234.5774	$234.58	$234.60	$234.60
Purchase #4	$39.52	6.867%	$42.2338	$42.23	$42.25	$42.20
Purchase #5	$98.36	10.650%	$108.8353	$108.84	$108.85	$108.80
Purchase #6	$112.43	7.245%	$120.5756	$120.58	$120.60	$120.60
Purchase #7	$189.27	10.151%	$208.4828	$208.48	$208.50	$208.50
7 purchase totals =	$1,025.56		$1,113.6076	$1,113.61	$1,113.70	$1,113.60