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	$202.76	10.688%	$224.431	$224.43	$224.45	$224.40
Purchase #2	$76.36	13.714%	$86.832	$86.83	$86.85	$86.80
Purchase #3	$22.39	8.466%	$24.2855	$24.29	$24.30	$24.30
Purchase #4	$139.31	3.549%	$144.2541	$144.25	$144.25	$144.30
Purchase #5	$154.40	11.748%	$172.5389	$172.54	$172.55	$172.50
Purchase #6	$208.97	3.228%	$215.7156	$215.72	$215.70	$215.70
Purchase #7	$101.54	7.751%	$109.4104	$109.41	$109.40	$109.40
7 purchase totals =	$905.73		$977.4675	$977.47	$977.50	$977.40