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	$154.38	8.573%	$167.615	$167.62	$167.60	$167.60
Purchase #2	$141.25	12.160%	$158.426	$158.43	$158.45	$158.40
Purchase #3	$59.36	13.232%	$67.2145	$67.21	$67.20	$67.20
Purchase #4	$216.29	13.575%	$245.6514	$245.65	$245.65	$245.70
Purchase #5	$62.33	4.382%	$65.0613	$65.06	$65.05	$65.10
Purchase #6	$111.83	12.554%	$125.8691	$125.87	$125.85	$125.90
Purchase #7	$157.34	7.139%	$168.5725	$168.57	$168.55	$168.60
7 purchase totals =	$902.78		$998.4098	$998.41	$998.35	$998.50