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	$92.86	11.330%	$103.381	$103.38	$103.40	$103.40
Purchase #2	$182.66	4.173%	$190.2824	$190.28	$190.30	$190.30
Purchase #3	$30.93	3.193%	$31.9176	$31.92	$31.90	$31.90
Purchase #4	$85.64	5.462%	$90.3177	$90.32	$90.30	$90.30
Purchase #5	$182.53	4.559%	$190.8515	$190.85	$190.85	$190.90
Purchase #6	$182.77	10.354%	$201.694	$201.69	$201.70	$201.70
Purchase #7	$176.64	10.153%	$194.5743	$194.57	$194.55	$194.60
7 purchase totals =	$934.03		$1,003.0185	$1,003.01	$1,003.00	$1,003.10