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	$82.41	13.586%	$93.6062	$93.61	$93.60	$93.60
Purchase #2	$199.67	6.782%	$213.2116	$213.21	$213.20	$213.20
Purchase #3	$19.46	12.153%	$21.825	$21.83	$21.85	$21.80
Purchase #4	$85.96	3.739%	$89.174	$89.17	$89.15	$89.20
Purchase #5	$145.94	4.783%	$152.9203	$152.92	$152.90	$152.90
Purchase #6	$15.42	12.704%	$17.379	$17.38	$17.40	$17.40
Purchase #7	$119.41	11.803%	$133.504	$133.50	$133.50	$133.50
7 purchase totals =	$668.27		$721.6201	$721.62	$721.60	$721.60