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	$105.51	12.732%	$118.9435	$118.94	$118.95	$118.90
Purchase #2	$196.40	9.872%	$215.7886	$215.79	$215.80	$215.80
Purchase #3	$94.49	6.122%	$100.2747	$100.27	$100.25	$100.30
Purchase #4	$85.42	10.140%	$94.0816	$94.08	$94.10	$94.10
Purchase #5	$106.47	11.167%	$118.3595	$118.36	$118.35	$118.40
Purchase #6	$68.32	12.284%	$76.7124	$76.71	$76.70	$76.70
Purchase #7	$93.94	9.659%	$103.0137	$103.01	$103.00	$103.00
7 purchase totals =	$750.55		$827.1740	$827.16	$827.15	$827.20