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	$63.79	13.791%	$72.5873	$72.59	$72.60	$72.60
Purchase #2	$83.26	7.536%	$89.5345	$89.53	$89.55	$89.50
Purchase #3	$85.68	10.848%	$94.9746	$94.97	$94.95	$95.00
Purchase #4	$177.31	11.844%	$198.3106	$198.31	$198.30	$198.30
Purchase #5	$133.31	8.334%	$144.4201	$144.42	$144.40	$144.40
Purchase #6	$133.66	4.499%	$139.6734	$139.67	$139.65	$139.70
Purchase #7	$16.67	13.363%	$18.8976	$18.90	$18.90	$18.90
7 purchase totals =	$693.68		$758.3981	$758.39	$758.35	$758.40