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	$114.41	3.421%	$118.324	$118.32	$118.30	$118.30
Purchase #2	$131.91	9.408%	$144.3201	$144.32	$144.30	$144.30
Purchase #3	$160.90	13.451%	$182.5427	$182.54	$182.55	$182.50
Purchase #4	$93.88	9.245%	$102.5592	$102.56	$102.55	$102.60
Purchase #5	$48.87	12.587%	$55.0213	$55.02	$55.00	$55.00
Purchase #6	$173.85	12.761%	$196.035	$196.04	$196.05	$196.00
Purchase #7	$93.49	3.769%	$97.0136	$97.01	$97.00	$97.00
7 purchase totals =	$817.31		$895.8159	$895.81	$895.75	$895.70