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	$9.86	6.463%	$10.4973	$10.50	$10.50	$10.50
Purchase #2	$161.99	8.270%	$175.3866	$175.39	$175.40	$175.40
Purchase #3	$62.37	5.291%	$65.67	$65.67	$65.65	$65.70
Purchase #4	$168.48	8.210%	$182.3122	$182.31	$182.30	$182.30
Purchase #5	$185.48	7.252%	$198.931	$198.93	$198.95	$198.90
Purchase #6	$33.71	6.349%	$35.8502	$35.85	$35.85	$35.90
Purchase #7	$29.94	5.496%	$31.5855	$31.59	$31.60	$31.60
7 purchase totals =	$651.83		$700.2328	$700.24	$700.25	$700.30