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	$150.60	9.292%	$164.5938	$164.59	$164.60	$164.60
Purchase #2	$62.63	6.188%	$66.5055	$66.51	$66.50	$66.50
Purchase #3	$17.68	13.807%	$20.1211	$20.12	$20.10	$20.10
Purchase #4	$104.34	11.621%	$116.4654	$116.47	$116.45	$116.50
Purchase #5	$65.25	8.834%	$71.0142	$71.01	$71.00	$71.00
Purchase #6	$193.52	9.115%	$211.1593	$211.16	$211.15	$211.20
Purchase #7	$60.47	11.670%	$67.5268	$67.53	$67.55	$67.50
7 purchase totals =	$654.49		$717.3861	$717.39	$717.35	$717.40