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	$248.92	13.641%	$282.8752	$282.88	$282.90	$282.90
Purchase #2	$201.71	11.269%	$224.4407	$224.44	$224.45	$224.40
Purchase #3	$158.63	3.363%	$163.9647	$163.96	$163.95	$164.00
Purchase #4	$169.78	12.414%	$190.8565	$190.86	$190.85	$190.90
Purchase #5	$54.50	12.789%	$61.47	$61.47	$61.45	$61.50
Purchase #6	$144.43	13.576%	$164.0378	$164.04	$164.05	$164.00
Purchase #7	$39.82	7.703%	$42.8873	$42.89	$42.90	$42.90
7 purchase totals =	$1,017.79		$1,130.5322	$1,130.54	$1,130.55	$1,130.60