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	$123.47	7.719%	$133.0006	$133.00	$133.00	$133.00
Purchase #2	$129.68	6.638%	$138.2882	$138.29	$138.30	$138.30
Purchase #3	$40.65	12.168%	$45.5963	$45.60	$45.60	$45.60
Purchase #4	$164.55	4.853%	$172.5356	$172.54	$172.55	$172.50
Purchase #5	$191.38	13.179%	$216.602	$216.60	$216.60	$216.60
Purchase #6	$23.41	5.273%	$24.6444	$24.64	$24.65	$24.60
Purchase #7	$182.89	8.377%	$198.2107	$198.21	$198.20	$198.20
7 purchase totals =	$856.03		$928.8778	$928.88	$928.90	$928.80