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	$245.37	5.693%	$259.3389	$259.34	$259.35	$259.30
Purchase #2	$181.51	10.571%	$200.6974	$200.70	$200.70	$200.70
Purchase #3	$34.47	3.617%	$35.7168	$35.72	$35.70	$35.70
Purchase #4	$100.89	4.205%	$105.1324	$105.13	$105.15	$105.10
Purchase #5	$189.62	9.623%	$207.8671	$207.87	$207.85	$207.90
Purchase #6	$208.89	6.789%	$223.0715	$223.07	$223.05	$223.10
Purchase #7	$135.57	3.182%	$139.8838	$139.88	$139.90	$139.90
7 purchase totals =	$1,096.32		$1,171.7079	$1,171.71	$1,171.70	$1,171.70