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	$240.73	6.508%	$256.3967	$256.40	$256.40	$256.40
Purchase #2	$161.25	3.355%	$166.6599	$166.66	$166.65	$166.70
Purchase #3	$75.30	4.282%	$78.5243	$78.52	$78.50	$78.50
Purchase #4	$200.25	6.414%	$213.094	$213.09	$213.10	$213.10
Purchase #5	$16.85	6.288%	$17.9095	$17.91	$17.90	$17.90
Purchase #6	$23.30	9.518%	$25.5177	$25.52	$25.50	$25.50
Purchase #7	$239.67	8.871%	$260.9311	$260.93	$260.95	$260.90
7 purchase totals =	$957.35		$1,019.0332	$1,019.03	$1,019.00	$1,019.00