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	$56.55	5.307%	$59.5511	$59.55	$59.55	$59.60
Purchase #2	$118.27	7.704%	$127.3815	$127.38	$127.40	$127.40
Purchase #3	$213.45	11.402%	$237.7876	$237.79	$237.80	$237.80
Purchase #4	$29.52	11.268%	$32.8463	$32.85	$32.85	$32.80
Purchase #5	$113.34	6.597%	$120.817	$120.82	$120.80	$120.80
Purchase #6	$75.37	3.555%	$78.0494	$78.05	$78.05	$78.00
Purchase #7	$102.37	11.317%	$113.9552	$113.96	$113.95	$114.00
7 purchase totals =	$708.87		$770.3881	$770.40	$770.40	$770.40