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	$125.51	6.696%	$133.9141	$133.91	$133.90	$133.90
Purchase #2	$134.34	13.537%	$152.5256	$152.53	$152.55	$152.50
Purchase #3	$109.38	6.215%	$116.178	$116.18	$116.20	$116.20
Purchase #4	$154.62	4.718%	$161.915	$161.92	$161.90	$161.90
Purchase #5	$161.40	7.267%	$173.1289	$173.13	$173.15	$173.10
Purchase #6	$57.39	11.551%	$64.0191	$64.02	$64.00	$64.00
Purchase #7	$59.67	13.800%	$67.9045	$67.90	$67.90	$67.90
7 purchase totals =	$802.31		$869.5852	$869.59	$869.60	$869.50