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	$125.84	12.646%	$141.7537	$141.75	$141.75	$141.80
Purchase #2	$205.94	4.621%	$215.4565	$215.46	$215.45	$215.50
Purchase #3	$211.72	7.331%	$227.2412	$227.24	$227.25	$227.20
Purchase #4	$135.48	3.709%	$140.505	$140.51	$140.50	$140.50
Purchase #5	$162.50	12.354%	$182.5753	$182.58	$182.60	$182.60
Purchase #6	$64.67	8.582%	$70.22	$70.22	$70.20	$70.20
Purchase #7	$40.56	11.208%	$45.106	$45.11	$45.10	$45.10
7 purchase totals =	$946.71		$1,022.8577	$1,022.87	$1,022.85	$1,022.90