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 $175.95   10.117%   $193.7509   $193.75   $193.75   $193.80  
  Purchase #2 $94.98   12.249%   $106.6141   $106.61   $106.60   $106.60  
  Purchase #3 $187.52   7.246%   $201.1077   $201.11   $201.10   $201.10  
  Purchase #4 $169.29   9.707%   $185.723   $185.72   $185.70   $185.70  
  Purchase #5 $122.70   11.168%   $136.4031   $136.40   $136.40   $136.40  
  Purchase #6 $195.98   7.459%   $210.5981   $210.60   $210.60   $210.60  
  Purchase #7 $21.81   13.709%   $24.7999   $24.80   $24.80   $24.80  
  7 purchase totals = $968.23       $1,058.9968   $1,058.99   $1,058.95   $1,059.00