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	$213.86	4.504%	$223.4923	$223.49	$223.50	$223.50
Purchase #2	$241.99	12.189%	$271.4862	$271.49	$271.50	$271.50
Purchase #3	$135.76	6.719%	$144.8817	$144.88	$144.90	$144.90
Purchase #4	$24.92	13.854%	$28.3724	$28.37	$28.35	$28.40
Purchase #5	$200.68	6.873%	$214.4727	$214.47	$214.45	$214.50
Purchase #6	$181.30	4.347%	$189.1811	$189.18	$189.20	$189.20
Purchase #7	$55.89	12.466%	$62.8572	$62.86	$62.85	$62.90
7 purchase totals =	$1,054.40		$1,134.7436	$1,134.74	$1,134.75	$1,134.90