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	$152.83	6.392%	$162.5989	$162.60	$162.60	$162.60
Purchase #2	$165.76	3.790%	$172.0423	$172.04	$172.05	$172.00
Purchase #3	$131.32	9.576%	$143.8952	$143.90	$143.90	$143.90
Purchase #4	$119.49	11.193%	$132.8645	$132.86	$132.85	$132.90
Purchase #5	$199.92	12.584%	$225.0779	$225.08	$225.10	$225.10
Purchase #6	$235.43	13.871%	$268.0865	$268.09	$268.10	$268.10
Purchase #7	$161.60	10.154%	$178.0089	$178.01	$178.00	$178.00
7 purchase totals =	$1,166.35		$1,282.5742	$1,282.58	$1,282.60	$1,282.60