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	$55.37	12.330%	$62.1971	$62.20	$62.20	$62.20
Purchase #2	$52.96	12.449%	$59.553	$59.55	$59.55	$59.60
Purchase #3	$203.37	4.360%	$212.2369	$212.24	$212.25	$212.20
Purchase #4	$240.67	8.615%	$261.4037	$261.40	$261.40	$261.40
Purchase #5	$28.92	9.469%	$31.6584	$31.66	$31.65	$31.70
Purchase #6	$127.53	3.364%	$131.8201	$131.82	$131.80	$131.80
Purchase #7	$38.52	9.238%	$42.0785	$42.08	$42.10	$42.10
7 purchase totals =	$747.34		$800.9477	$800.95	$800.95	$801.00