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	$189.36	9.681%	$207.6919	$207.69	$207.70	$207.70
Purchase #2	$131.30	9.646%	$143.9652	$143.97	$143.95	$144.00
Purchase #3	$6.30	4.665%	$6.5939	$6.59	$6.60	$6.60
Purchase #4	$88.96	6.683%	$94.9052	$94.91	$94.90	$94.90
Purchase #5	$98.72	6.611%	$105.2464	$105.25	$105.25	$105.20
Purchase #6	$40.33	12.701%	$45.4523	$45.45	$45.45	$45.50
Purchase #7	$12.92	7.265%	$13.8586	$13.86	$13.85	$13.90
7 purchase totals =	$567.89		$617.7135	$617.72	$617.70	$617.80