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	$178.67	3.561%	$185.0324	$185.03	$185.05	$185.00
Purchase #2	$202.36	9.423%	$221.4284	$221.43	$221.45	$221.40
Purchase #3	$118.54	10.635%	$131.1467	$131.15	$131.15	$131.10
Purchase #4	$126.84	3.684%	$131.5128	$131.51	$131.50	$131.50
Purchase #5	$94.86	10.484%	$104.8051	$104.81	$104.80	$104.80
Purchase #6	$156.91	6.664%	$167.3665	$167.37	$167.35	$167.40
Purchase #7	$227.50	4.248%	$237.1642	$237.16	$237.15	$237.20
7 purchase totals =	$1,105.68		$1,178.4561	$1,178.46	$1,178.45	$1,178.40