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	$152.38	12.533%	$171.4778	$171.48	$171.50	$171.50
Purchase #2	$44.69	7.140%	$47.8809	$47.88	$47.90	$47.90
Purchase #3	$190.82	7.478%	$205.0895	$205.09	$205.10	$205.10
Purchase #4	$213.40	4.262%	$222.4951	$222.50	$222.50	$222.50
Purchase #5	$60.30	12.723%	$67.972	$67.97	$67.95	$68.00
Purchase #6	$146.94	5.863%	$155.5551	$155.56	$155.55	$155.60
Purchase #7	$137.82	7.622%	$148.3246	$148.32	$148.30	$148.30
7 purchase totals =	$946.35		$1,018.7950	$1,018.80	$1,018.80	$1,018.90