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	$98.96	4.629%	$103.5409	$103.54	$103.55	$103.50
Purchase #2	$29.41	5.730%	$31.0952	$31.10	$31.10	$31.10
Purchase #3	$80.80	6.682%	$86.1991	$86.20	$86.20	$86.20
Purchase #4	$136.42	5.158%	$143.4565	$143.46	$143.45	$143.50
Purchase #5	$81.52	6.225%	$86.5946	$86.59	$86.60	$86.60
Purchase #6	$190.91	4.479%	$199.4609	$199.46	$199.45	$199.50
Purchase #7	$200.33	6.747%	$213.8463	$213.85	$213.85	$213.80
7 purchase totals =	$818.35		$864.1935	$864.20	$864.20	$864.20