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	$233.86	6.137%	$248.212	$248.21	$248.20	$248.20
Purchase #2	$179.72	9.517%	$196.824	$196.82	$196.80	$196.80
Purchase #3	$135.87	9.773%	$149.1486	$149.15	$149.15	$149.10
Purchase #4	$90.97	10.479%	$100.5027	$100.50	$100.50	$100.50
Purchase #5	$88.30	10.204%	$97.3101	$97.31	$97.30	$97.30
Purchase #6	$103.43	9.741%	$113.5051	$113.51	$113.50	$113.50
Purchase #7	$6.39	6.792%	$6.824	$6.82	$6.80	$6.80
7 purchase totals =	$838.54		$912.3265	$912.32	$912.25	$912.20