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	$184.54	7.415%	$198.2236	$198.22	$198.20	$198.20
Purchase #2	$171.40	6.461%	$182.4742	$182.47	$182.45	$182.50
Purchase #3	$208.83	6.571%	$222.5522	$222.55	$222.55	$222.60
Purchase #4	$88.51	13.223%	$100.2137	$100.21	$100.20	$100.20
Purchase #5	$80.70	12.595%	$90.8642	$90.86	$90.85	$90.90
Purchase #6	$68.91	6.482%	$73.3767	$73.38	$73.40	$73.40
Purchase #7	$194.85	5.336%	$205.2472	$205.25	$205.25	$205.20
7 purchase totals =	$997.74		$1,072.9518	$1,072.94	$1,072.90	$1,073.00