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	$242.97	7.189%	$260.4371	$260.44	$260.45	$260.40
Purchase #2	$86.95	3.453%	$89.9524	$89.95	$89.95	$90.00
Purchase #3	$59.53	11.701%	$66.4956	$66.50	$66.50	$66.50
Purchase #4	$117.85	9.427%	$128.9597	$128.96	$128.95	$129.00
Purchase #5	$43.56	4.329%	$45.4457	$45.45	$45.45	$45.40
Purchase #6	$21.68	4.832%	$22.7276	$22.73	$22.75	$22.70
Purchase #7	$160.47	7.653%	$172.7508	$172.75	$172.75	$172.80
7 purchase totals =	$733.01		$786.7689	$786.78	$786.80	$786.80