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	$152.87	10.861%	$169.4732	$169.47	$169.45	$169.50
Purchase #2	$35.40	9.732%	$38.8451	$38.85	$38.85	$38.80
Purchase #3	$205.83	4.470%	$215.0306	$215.03	$215.05	$215.00
Purchase #4	$232.59	5.426%	$245.2103	$245.21	$245.20	$245.20
Purchase #5	$34.86	6.807%	$37.2329	$37.23	$37.25	$37.20
Purchase #6	$217.54	9.310%	$237.793	$237.79	$237.80	$237.80
Purchase #7	$39.93	8.469%	$43.3117	$43.31	$43.30	$43.30
7 purchase totals =	$919.02		$986.8968	$986.89	$986.90	$986.80