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	$68.86	5.411%	$72.586	$72.59	$72.60	$72.60
Purchase #2	$168.79	6.327%	$179.4693	$179.47	$179.45	$179.50
Purchase #3	$230.48	5.366%	$242.8476	$242.85	$242.85	$242.80
Purchase #4	$20.92	12.279%	$23.4888	$23.49	$23.50	$23.50
Purchase #5	$140.88	11.103%	$156.5219	$156.52	$156.50	$156.50
Purchase #6	$102.33	10.445%	$113.0184	$113.02	$113.00	$113.00
Purchase #7	$131.81	11.344%	$146.7625	$146.76	$146.75	$146.80
7 purchase totals =	$864.07		$934.6945	$934.70	$934.65	$934.70