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	$123.46	8.125%	$133.4911	$133.49	$133.50	$133.50
Purchase #2	$86.66	4.556%	$90.6082	$90.61	$90.60	$90.60
Purchase #3	$80.89	11.861%	$90.4844	$90.48	$90.50	$90.50
Purchase #4	$72.88	5.380%	$76.8009	$76.80	$76.80	$76.80
Purchase #5	$249.65	4.637%	$261.2263	$261.23	$261.25	$261.20
Purchase #6	$242.30	8.323%	$262.4666	$262.47	$262.45	$262.50
Purchase #7	$114.95	13.679%	$130.674	$130.67	$130.65	$130.70
7 purchase totals =	$970.79		$1,045.7515	$1,045.75	$1,045.75	$1,045.80