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	$210.77	6.297%	$224.0422	$224.04	$224.05	$224.00
Purchase #2	$71.82	11.484%	$80.0678	$80.07	$80.05	$80.10
Purchase #3	$151.36	11.587%	$168.8981	$168.90	$168.90	$168.90
Purchase #4	$152.85	13.751%	$173.8684	$173.87	$173.85	$173.90
Purchase #5	$108.50	5.494%	$114.461	$114.46	$114.45	$114.50
Purchase #6	$137.64	4.537%	$143.8847	$143.88	$143.90	$143.90
Purchase #7	$164.39	10.439%	$181.5507	$181.55	$181.55	$181.60
7 purchase totals =	$997.33		$1,086.7729	$1,086.77	$1,086.75	$1,086.90