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	$81.70	7.721%	$88.0081	$88.01	$88.00	$88.00
Purchase #2	$15.90	10.732%	$17.6064	$17.61	$17.60	$17.60
Purchase #3	$95.94	4.648%	$100.3993	$100.40	$100.40	$100.40
Purchase #4	$39.54	4.325%	$41.2501	$41.25	$41.25	$41.30
Purchase #5	$158.75	11.744%	$177.3936	$177.39	$177.40	$177.40
Purchase #6	$179.63	9.538%	$196.7631	$196.76	$196.75	$196.80
Purchase #7	$133.95	9.667%	$146.8989	$146.90	$146.90	$146.90
7 purchase totals =	$705.41		$768.3195	$768.32	$768.30	$768.40