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	$132.83	11.246%	$147.7681	$147.77	$147.75	$147.80
Purchase #2	$76.87	6.417%	$81.8027	$81.80	$81.80	$81.80
Purchase #3	$181.30	10.593%	$200.5051	$200.51	$200.50	$200.50
Purchase #4	$243.48	12.783%	$274.604	$274.60	$274.60	$274.60
Purchase #5	$7.85	6.791%	$8.3831	$8.38	$8.40	$8.40
Purchase #6	$150.51	3.151%	$155.2526	$155.25	$155.25	$155.30
Purchase #7	$51.55	5.294%	$54.2791	$54.28	$54.30	$54.30
7 purchase totals =	$844.39		$922.5947	$922.59	$922.60	$922.70