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	$235.86	10.189%	$259.8918	$259.89	$259.90	$259.90
Purchase #2	$72.58	11.848%	$81.1793	$81.18	$81.20	$81.20
Purchase #3	$18.78	7.763%	$20.2379	$20.24	$20.25	$20.20
Purchase #4	$187.67	4.690%	$196.4717	$196.47	$196.45	$196.50
Purchase #5	$29.63	7.644%	$31.8949	$31.89	$31.90	$31.90
Purchase #6	$131.57	12.185%	$147.6018	$147.60	$147.60	$147.60
Purchase #7	$230.37	5.545%	$243.144	$243.14	$243.15	$243.10
7 purchase totals =	$906.46		$980.4214	$980.41	$980.45	$980.40