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	$85.84	6.536%	$91.4505	$91.45	$91.45	$91.50
Purchase #2	$87.86	9.147%	$95.8966	$95.90	$95.90	$95.90
Purchase #3	$76.26	11.809%	$85.2655	$85.27	$85.25	$85.30
Purchase #4	$56.45	12.620%	$63.574	$63.57	$63.55	$63.60
Purchase #5	$76.41	13.781%	$86.9401	$86.94	$86.95	$86.90
Purchase #6	$93.66	5.203%	$98.5331	$98.53	$98.55	$98.50
Purchase #7	$30.98	11.605%	$34.5752	$34.58	$34.60	$34.60
7 purchase totals =	$507.46		$556.2350	$556.24	$556.25	$556.30