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	$218.64	8.328%	$236.8483	$236.85	$236.85	$236.80
Purchase #2	$34.32	11.817%	$38.3756	$38.38	$38.40	$38.40
Purchase #3	$138.84	12.436%	$156.1061	$156.11	$156.10	$156.10
Purchase #4	$121.50	13.365%	$137.7385	$137.74	$137.75	$137.70
Purchase #5	$153.93	9.479%	$168.521	$168.52	$168.50	$168.50
Purchase #6	$233.76	11.660%	$261.0164	$261.02	$261.00	$261.00
Purchase #7	$16.87	6.129%	$17.904	$17.90	$17.90	$17.90
7 purchase totals =	$917.86		$1,016.5099	$1,016.52	$1,016.50	$1,016.40