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	$119.66	9.815%	$131.4046	$131.40	$131.40	$131.40
Purchase #2	$38.48	10.841%	$42.6516	$42.65	$42.65	$42.70
Purchase #3	$48.89	8.211%	$52.9044	$52.90	$52.90	$52.90
Purchase #4	$93.78	6.432%	$99.8119	$99.81	$99.80	$99.80
Purchase #5	$171.47	12.222%	$192.4271	$192.43	$192.45	$192.40
Purchase #6	$183.89	10.206%	$202.6578	$202.66	$202.65	$202.70
Purchase #7	$27.91	13.482%	$31.6728	$31.67	$31.65	$31.70
7 purchase totals =	$684.08		$753.5302	$753.52	$753.50	$753.60