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	$147.85	3.212%	$152.5989	$152.60	$152.60	$152.60
Purchase #2	$71.46	12.468%	$80.3696	$80.37	$80.35	$80.40
Purchase #3	$82.37	5.590%	$86.9745	$86.97	$86.95	$87.00
Purchase #4	$159.41	10.779%	$176.5928	$176.59	$176.60	$176.60
Purchase #5	$37.79	12.665%	$42.5761	$42.58	$42.60	$42.60
Purchase #6	$123.90	7.165%	$132.7774	$132.78	$132.80	$132.80
Purchase #7	$138.95	10.790%	$153.9427	$153.94	$153.95	$153.90
7 purchase totals =	$761.73		$825.8320	$825.83	$825.85	$825.90