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 $87.34   5.350%   $92.0127   $92.01   $92.00   $92.00  
  Purchase #2 $162.43   7.556%   $174.7032   $174.70   $174.70   $174.70  
  Purchase #3 $60.27   4.613%   $63.0503   $63.05   $63.05   $63.10  
  Purchase #4 $189.97   10.382%   $209.6927   $209.69   $209.70   $209.70  
  Purchase #5 $185.98   6.257%   $197.6168   $197.62   $197.60   $197.60  
  Purchase #6 $175.34   10.482%   $193.7191   $193.72   $193.70   $193.70  
  Purchase #7 $11.58   13.412%   $13.1331   $13.13   $13.15   $13.10  
  7 purchase totals = $872.91       $943.9279   $943.92   $943.90   $943.90