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	$82.29	12.448%	$92.5335	$92.53	$92.55	$92.50
Purchase #2	$135.34	12.247%	$151.9151	$151.92	$151.90	$151.90
Purchase #3	$29.58	9.357%	$32.3478	$32.35	$32.35	$32.30
Purchase #4	$212.77	10.714%	$235.5662	$235.57	$235.55	$235.60
Purchase #5	$81.59	6.230%	$86.6731	$86.67	$86.65	$86.70
Purchase #6	$181.55	8.151%	$196.3481	$196.35	$196.35	$196.30
Purchase #7	$140.31	5.781%	$148.4213	$148.42	$148.40	$148.40
7 purchase totals =	$863.43		$943.8051	$943.81	$943.75	$943.70