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	$143.55	13.189%	$162.4828	$162.48	$162.50	$162.50
Purchase #2	$49.71	10.604%	$54.9812	$54.98	$55.00	$55.00
Purchase #3	$150.77	3.503%	$156.0515	$156.05	$156.05	$156.10
Purchase #4	$151.98	10.574%	$168.0504	$168.05	$168.05	$168.10
Purchase #5	$9.74	8.589%	$10.5766	$10.58	$10.60	$10.60
Purchase #6	$217.46	12.256%	$244.1119	$244.11	$244.10	$244.10
Purchase #7	$202.83	12.778%	$228.7476	$228.75	$228.75	$228.70
7 purchase totals =	$926.04		$1,025.0020	$1,025.00	$1,025.05	$1,025.10