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	$33.29	12.599%	$37.4842	$37.48	$37.50	$37.50
Purchase #2	$100.54	9.149%	$109.7384	$109.74	$109.75	$109.70
Purchase #3	$31.26	10.130%	$34.4266	$34.43	$34.45	$34.40
Purchase #4	$144.43	3.639%	$149.6858	$149.69	$149.70	$149.70
Purchase #5	$180.39	5.659%	$190.5983	$190.60	$190.60	$190.60
Purchase #6	$243.52	3.515%	$252.0797	$252.08	$252.10	$252.10
Purchase #7	$217.98	7.140%	$233.5438	$233.54	$233.55	$233.50
7 purchase totals =	$951.41		$1,007.5568	$1,007.56	$1,007.65	$1,007.50