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	$243.59	7.648%	$262.2198	$262.22	$262.20	$262.20
Purchase #2	$205.60	10.419%	$227.0215	$227.02	$227.00	$227.00
Purchase #3	$36.56	3.823%	$37.9577	$37.96	$37.95	$38.00
Purchase #4	$148.95	10.291%	$164.2784	$164.28	$164.30	$164.30
Purchase #5	$246.78	7.745%	$265.8931	$265.89	$265.90	$265.90
Purchase #6	$13.83	9.129%	$15.0925	$15.09	$15.10	$15.10
Purchase #7	$160.90	3.709%	$166.8678	$166.87	$166.85	$166.90
7 purchase totals =	$1,056.21		$1,139.3308	$1,139.33	$1,139.30	$1,139.40