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	$217.51	3.763%	$225.6949	$225.69	$225.70	$225.70
Purchase #2	$96.83	13.371%	$109.7771	$109.78	$109.80	$109.80
Purchase #3	$146.92	10.558%	$162.4318	$162.43	$162.45	$162.40
Purchase #4	$208.78	11.393%	$232.5663	$232.57	$232.55	$232.60
Purchase #5	$219.30	11.540%	$244.6072	$244.61	$244.60	$244.60
Purchase #6	$135.73	5.654%	$143.4042	$143.40	$143.40	$143.40
Purchase #7	$30.55	3.248%	$31.5423	$31.54	$31.55	$31.50
7 purchase totals =	$1,055.62		$1,150.0238	$1,150.02	$1,150.05	$1,150.00