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	$31.50	6.410%	$33.5192	$33.52	$33.50	$33.50
Purchase #2	$164.72	13.859%	$187.5485	$187.55	$187.55	$187.50
Purchase #3	$177.73	7.289%	$190.6847	$190.68	$190.70	$190.70
Purchase #4	$89.55	10.395%	$98.8587	$98.86	$98.85	$98.90
Purchase #5	$135.78	11.335%	$151.1707	$151.17	$151.15	$151.20
Purchase #6	$184.73	12.445%	$207.7196	$207.72	$207.70	$207.70
Purchase #7	$163.33	11.440%	$182.015	$182.02	$182.00	$182.00
7 purchase totals =	$947.34		$1,051.5164	$1,051.52	$1,051.45	$1,051.50