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	$126.82	11.548%	$141.4652	$141.47	$141.45	$141.50
Purchase #2	$96.58	6.285%	$102.6501	$102.65	$102.65	$102.70
Purchase #3	$141.54	6.104%	$150.1796	$150.18	$150.20	$150.20
Purchase #4	$162.61	8.248%	$176.0221	$176.02	$176.00	$176.00
Purchase #5	$60.37	11.867%	$67.5341	$67.53	$67.55	$67.50
Purchase #6	$105.84	11.863%	$118.3958	$118.40	$118.40	$118.40
Purchase #7	$55.38	12.807%	$62.4725	$62.47	$62.45	$62.50
7 purchase totals =	$749.14		$818.7194	$818.72	$818.70	$818.80