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	$64.39	4.183%	$67.0834	$67.08	$67.10	$67.10
Purchase #2	$139.89	9.151%	$152.6913	$152.69	$152.70	$152.70
Purchase #3	$116.60	8.808%	$126.8701	$126.87	$126.85	$126.90
Purchase #4	$42.79	6.439%	$45.5452	$45.55	$45.55	$45.50
Purchase #5	$24.43	6.296%	$25.9681	$25.97	$25.95	$26.00
Purchase #6	$13.37	11.586%	$14.919	$14.92	$14.90	$14.90
Purchase #7	$57.33	5.595%	$60.5376	$60.54	$60.55	$60.50
7 purchase totals =	$458.80		$493.6147	$493.62	$493.60	$493.60