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	$126.73	7.367%	$136.0662	$136.07	$136.05	$136.10
Purchase #2	$46.80	6.549%	$49.8649	$49.86	$49.85	$49.90
Purchase #3	$33.51	9.475%	$36.6851	$36.69	$36.70	$36.70
Purchase #4	$168.86	11.260%	$187.8736	$187.87	$187.85	$187.90
Purchase #5	$77.47	6.660%	$82.6295	$82.63	$82.65	$82.60
Purchase #6	$80.39	6.825%	$85.8766	$85.88	$85.90	$85.90
Purchase #7	$136.39	4.516%	$142.5494	$142.55	$142.55	$142.50
7 purchase totals =	$670.15		$721.5453	$721.55	$721.55	$721.60