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	$183.47	9.208%	$200.3639	$200.36	$200.35	$200.40
Purchase #2	$29.83	6.462%	$31.7576	$31.76	$31.75	$31.80
Purchase #3	$109.25	7.775%	$117.7442	$117.74	$117.75	$117.70
Purchase #4	$92.83	6.784%	$99.1276	$99.13	$99.15	$99.10
Purchase #5	$87.50	12.215%	$98.1881	$98.19	$98.20	$98.20
Purchase #6	$62.32	6.701%	$66.4961	$66.50	$66.50	$66.50
Purchase #7	$238.63	3.868%	$247.8602	$247.86	$247.85	$247.90
7 purchase totals =	$803.83		$861.5377	$861.54	$861.55	$861.60