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	$93.83	10.193%	$103.3941	$103.39	$103.40	$103.40
Purchase #2	$160.48	9.827%	$176.2504	$176.25	$176.25	$176.30
Purchase #3	$187.97	6.840%	$200.8271	$200.83	$200.85	$200.80
Purchase #4	$236.87	13.333%	$268.4519	$268.45	$268.45	$268.50
Purchase #5	$122.91	6.749%	$131.2052	$131.21	$131.20	$131.20
Purchase #6	$207.83	9.172%	$226.8922	$226.89	$226.90	$226.90
Purchase #7	$42.61	8.506%	$46.2344	$46.23	$46.25	$46.20
7 purchase totals =	$1,052.50		$1,153.2553	$1,153.25	$1,153.30	$1,153.30