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	$245.40	10.502%	$271.1719	$271.17	$271.15	$271.20
Purchase #2	$84.27	3.764%	$87.4419	$87.44	$87.45	$87.40
Purchase #3	$37.48	13.410%	$42.5061	$42.51	$42.50	$42.50
Purchase #4	$98.67	13.309%	$111.802	$111.80	$111.80	$111.80
Purchase #5	$154.85	5.783%	$163.805	$163.81	$163.80	$163.80
Purchase #6	$32.56	3.186%	$33.5974	$33.60	$33.60	$33.60
Purchase #7	$44.28	7.756%	$47.7144	$47.71	$47.70	$47.70
7 purchase totals =	$697.51		$758.0387	$758.04	$758.00	$758.00