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	$98.72	10.418%	$109.0046	$109.00	$109.00	$109.00
Purchase #2	$27.69	13.183%	$31.3404	$31.34	$31.35	$31.30
Purchase #3	$53.37	11.368%	$59.4371	$59.44	$59.45	$59.40
Purchase #4	$34.85	5.509%	$36.7699	$36.77	$36.75	$36.80
Purchase #5	$160.97	6.785%	$171.8918	$171.89	$171.90	$171.90
Purchase #6	$190.97	9.190%	$208.5201	$208.52	$208.50	$208.50
Purchase #7	$128.81	11.228%	$143.2728	$143.27	$143.25	$143.30
7 purchase totals =	$695.38		$760.2367	$760.23	$760.20	$760.20