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	$233.37	7.482%	$250.8307	$250.83	$250.85	$250.80
Purchase #2	$169.79	12.168%	$190.45	$190.45	$190.45	$190.50
Purchase #3	$235.69	10.837%	$261.2317	$261.23	$261.25	$261.20
Purchase #4	$163.95	13.765%	$186.5177	$186.52	$186.50	$186.50
Purchase #5	$99.60	8.642%	$108.2074	$108.21	$108.20	$108.20
Purchase #6	$131.61	9.278%	$143.8208	$143.82	$143.80	$143.80
Purchase #7	$50.83	9.233%	$55.5231	$55.52	$55.50	$55.50
7 purchase totals =	$1,084.84		$1,196.5814	$1,196.58	$1,196.55	$1,196.50