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	$245.95	3.774%	$255.2322	$255.23	$255.25	$255.20
Purchase #2	$198.34	9.793%	$217.7634	$217.76	$217.75	$217.80
Purchase #3	$161.94	9.135%	$176.7332	$176.73	$176.75	$176.70
Purchase #4	$134.88	6.647%	$143.8455	$143.85	$143.85	$143.80
Purchase #5	$50.54	9.710%	$55.4474	$55.45	$55.45	$55.40
Purchase #6	$89.27	3.136%	$92.0695	$92.07	$92.05	$92.10
Purchase #7	$223.48	3.588%	$231.4985	$231.50	$231.50	$231.50
7 purchase totals =	$1,104.40		$1,172.5897	$1,172.59	$1,172.60	$1,172.50