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 $239.34   9.402%   $261.8427   $261.84   $261.85   $261.80  
  Purchase #2 $47.95   13.450%   $54.3993   $54.40   $54.40   $54.40  
  Purchase #3 $106.49   5.796%   $112.6622   $112.66   $112.65   $112.70  
  Purchase #4 $188.44   5.144%   $198.1334   $198.13   $198.15   $198.10  
  Purchase #5 $75.65   12.649%   $85.219   $85.22   $85.20   $85.20  
  Purchase #6 $141.86   4.147%   $147.7429   $147.74   $147.75   $147.70  
  Purchase #7 $226.52   4.347%   $236.3668   $236.37   $236.35   $236.40  
  7 purchase totals = $1,026.25       $1,096.3663   $1,096.36   $1,096.35   $1,096.30