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	$66.70	9.175%	$72.8197	$72.82	$72.80	$72.80
Purchase #2	$56.39	12.756%	$63.5831	$63.58	$63.60	$63.60
Purchase #3	$160.88	3.494%	$166.5011	$166.50	$166.50	$166.50
Purchase #4	$164.42	3.354%	$169.9346	$169.93	$169.95	$169.90
Purchase #5	$184.67	6.523%	$196.716	$196.72	$196.70	$196.70
Purchase #6	$49.38	5.620%	$52.1552	$52.16	$52.15	$52.20
Purchase #7	$106.56	13.465%	$120.9083	$120.91	$120.90	$120.90
7 purchase totals =	$789.00		$842.6180	$842.62	$842.60	$842.60