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	$82.94	5.430%	$87.4436	$87.44	$87.45	$87.40
Purchase #2	$190.57	3.353%	$196.9598	$196.96	$196.95	$197.00
Purchase #3	$153.34	3.621%	$158.8924	$158.89	$158.90	$158.90
Purchase #4	$120.28	9.182%	$131.3241	$131.32	$131.30	$131.30
Purchase #5	$166.67	11.476%	$185.797	$185.80	$185.80	$185.80
Purchase #6	$37.78	3.738%	$39.1922	$39.19	$39.20	$39.20
Purchase #7	$65.78	7.842%	$70.9385	$70.94	$70.95	$70.90
7 purchase totals =	$817.36		$870.5476	$870.54	$870.55	$870.50