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	$92.48	12.354%	$103.905	$103.91	$103.90	$103.90
Purchase #2	$11.61	11.841%	$12.9847	$12.98	$13.00	$13.00
Purchase #3	$41.90	4.106%	$43.6204	$43.62	$43.60	$43.60
Purchase #4	$31.56	4.810%	$33.078	$33.08	$33.10	$33.10
Purchase #5	$225.60	9.147%	$246.2356	$246.24	$246.25	$246.20
Purchase #6	$169.67	3.466%	$175.5508	$175.55	$175.55	$175.60
Purchase #7	$44.67	11.625%	$49.8629	$49.86	$49.85	$49.90
7 purchase totals =	$617.49		$665.2374	$665.24	$665.25	$665.30