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	$123.39	9.324%	$134.8949	$134.89	$134.90	$134.90
Purchase #2	$121.62	12.196%	$136.4528	$136.45	$136.45	$136.50
Purchase #3	$99.37	3.554%	$102.9016	$102.90	$102.90	$102.90
Purchase #4	$110.38	12.362%	$124.0252	$124.03	$124.05	$124.00
Purchase #5	$198.77	13.497%	$225.598	$225.60	$225.60	$225.60
Purchase #6	$96.31	13.787%	$109.5883	$109.59	$109.60	$109.60
Purchase #7	$222.74	11.553%	$248.4732	$248.47	$248.45	$248.50
7 purchase totals =	$972.58		$1,081.9340	$1,081.93	$1,081.95	$1,082.00