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	$85.65	10.193%	$94.3803	$94.38	$94.40	$94.40
Purchase #2	$46.67	9.696%	$51.1951	$51.20	$51.20	$51.20
Purchase #3	$248.45	13.689%	$282.4603	$282.46	$282.45	$282.50
Purchase #4	$124.72	13.610%	$141.6944	$141.69	$141.70	$141.70
Purchase #5	$130.62	8.626%	$141.8873	$141.89	$141.90	$141.90
Purchase #6	$54.42	11.123%	$60.4731	$60.47	$60.45	$60.50
Purchase #7	$161.34	13.303%	$182.8031	$182.80	$182.80	$182.80
7 purchase totals =	$851.87		$954.8936	$954.89	$954.90	$955.00