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	$128.29	9.688%	$140.7187	$140.72	$140.70	$140.70
Purchase #2	$169.96	7.644%	$182.9517	$182.95	$182.95	$183.00
Purchase #3	$238.67	10.418%	$263.5346	$263.53	$263.55	$263.50
Purchase #4	$59.90	12.644%	$67.4738	$67.47	$67.45	$67.50
Purchase #5	$141.38	4.687%	$148.0065	$148.01	$148.00	$148.00
Purchase #6	$39.85	13.151%	$45.0907	$45.09	$45.10	$45.10
Purchase #7	$120.48	6.191%	$127.9389	$127.94	$127.95	$127.90
7 purchase totals =	$898.53		$975.7149	$975.71	$975.70	$975.70