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	$216.89	13.211%	$245.5433	$245.54	$245.55	$245.50
Purchase #2	$189.30	10.734%	$209.6195	$209.62	$209.60	$209.60
Purchase #3	$77.77	8.691%	$84.529	$84.53	$84.55	$84.50
Purchase #4	$92.81	8.746%	$100.9272	$100.93	$100.95	$100.90
Purchase #5	$6.91	3.268%	$7.1358	$7.14	$7.15	$7.10
Purchase #6	$72.47	8.412%	$78.5662	$78.57	$78.55	$78.60
Purchase #7	$243.43	5.824%	$257.6074	$257.61	$257.60	$257.60
7 purchase totals =	$899.58		$983.9284	$983.94	$983.95	$983.80