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	$126.60	11.164%	$140.7336	$140.73	$140.75	$140.70
Purchase #2	$207.71	5.176%	$218.4611	$218.46	$218.45	$218.50
Purchase #3	$222.93	8.508%	$241.8969	$241.90	$241.90	$241.90
Purchase #4	$58.44	13.774%	$66.4895	$66.49	$66.50	$66.50
Purchase #5	$166.83	7.726%	$179.7193	$179.72	$179.70	$179.70
Purchase #6	$126.42	11.517%	$140.9798	$140.98	$141.00	$141.00
Purchase #7	$76.42	12.139%	$85.6966	$85.70	$85.70	$85.70
7 purchase totals =	$985.35		$1,073.9768	$1,073.98	$1,074.00	$1,074.00