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	$66.64	7.706%	$71.7753	$71.78	$71.80	$71.80
Purchase #2	$29.93	7.185%	$32.0805	$32.08	$32.10	$32.10
Purchase #3	$101.99	12.650%	$114.8917	$114.89	$114.90	$114.90
Purchase #4	$234.83	5.433%	$247.5883	$247.59	$247.60	$247.60
Purchase #5	$182.38	7.313%	$195.7174	$195.72	$195.70	$195.70
Purchase #6	$18.42	13.536%	$20.9133	$20.91	$20.90	$20.90
Purchase #7	$199.46	8.427%	$216.2685	$216.27	$216.25	$216.30
7 purchase totals =	$833.65		$899.2350	$899.24	$899.25	$899.30