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	$143.87	5.491%	$151.7699	$151.77	$151.75	$151.80
Purchase #2	$85.91	5.228%	$90.4014	$90.40	$90.40	$90.40
Purchase #3	$55.95	13.704%	$63.6174	$63.62	$63.60	$63.60
Purchase #4	$71.56	9.565%	$78.4047	$78.40	$78.40	$78.40
Purchase #5	$44.76	9.451%	$48.9903	$48.99	$49.00	$49.00
Purchase #6	$113.50	5.601%	$119.8571	$119.86	$119.85	$119.90
Purchase #7	$193.37	3.373%	$199.8924	$199.89	$199.90	$199.90
7 purchase totals =	$708.92		$752.9332	$752.93	$752.90	$753.00