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 $195.48   3.205%   $201.7451   $201.75   $201.75   $201.70  
  Purchase #2 $232.78   12.247%   $261.2886   $261.29   $261.30   $261.30  
  Purchase #3 $43.74   7.745%   $47.1277   $47.13   $47.15   $47.10  
  Purchase #4 $112.88   12.521%   $127.0137   $127.01   $127.00   $127.00  
  Purchase #5 $228.79   9.594%   $250.7401   $250.74   $250.75   $250.70  
  Purchase #6 $41.47   13.458%   $47.051   $47.05   $47.05   $47.10  
  Purchase #7 $21.58   7.109%   $23.1141   $23.11   $23.10   $23.10  
  7 purchase totals = $876.72       $958.0803   $958.08   $958.10   $958.00