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	$145.67	3.238%	$150.3868	$150.39	$150.40	$150.40
Purchase #2	$21.46	11.184%	$23.8601	$23.86	$23.85	$23.90
Purchase #3	$195.86	7.845%	$211.2252	$211.23	$211.25	$211.20
Purchase #4	$182.90	4.325%	$190.8104	$190.81	$190.80	$190.80
Purchase #5	$108.57	3.391%	$112.2516	$112.25	$112.25	$112.30
Purchase #6	$59.97	7.677%	$64.5739	$64.57	$64.55	$64.60
Purchase #7	$135.82	6.339%	$144.4296	$144.43	$144.45	$144.40
7 purchase totals =	$850.25		$897.5376	$897.54	$897.55	$897.60