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	$163.94	13.673%	$186.3555	$186.36	$186.35	$186.40
Purchase #2	$155.88	5.682%	$164.7371	$164.74	$164.75	$164.70
Purchase #3	$222.57	5.844%	$235.577	$235.58	$235.60	$235.60
Purchase #4	$178.29	12.429%	$200.4497	$200.45	$200.45	$200.40
Purchase #5	$63.77	3.412%	$65.9458	$65.95	$65.95	$65.90
Purchase #6	$69.74	5.192%	$73.3609	$73.36	$73.35	$73.40
Purchase #7	$132.96	13.156%	$150.4522	$150.45	$150.45	$150.50
7 purchase totals =	$987.15		$1,076.8782	$1,076.89	$1,076.90	$1,076.90