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	$107.58	8.301%	$116.5102	$116.51	$116.50	$116.50
Purchase #2	$238.60	9.220%	$260.5989	$260.60	$260.60	$260.60
Purchase #3	$68.98	7.201%	$73.9472	$73.95	$73.95	$73.90
Purchase #4	$27.46	12.485%	$30.8884	$30.89	$30.90	$30.90
Purchase #5	$110.82	11.259%	$123.2972	$123.30	$123.30	$123.30
Purchase #6	$6.64	13.482%	$7.5352	$7.54	$7.55	$7.50
Purchase #7	$109.55	4.345%	$114.3099	$114.31	$114.30	$114.30
7 purchase totals =	$669.63		$727.0870	$727.10	$727.10	$727.00