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 $23.49   6.209%   $24.9485   $24.95   $24.95   $24.90  
  Purchase #2 $225.89   9.140%   $246.5363   $246.54   $246.55   $246.50  
  Purchase #3 $169.97   7.443%   $182.6209   $182.62   $182.60   $182.60  
  Purchase #4 $26.67   6.412%   $28.3801   $28.38   $28.40   $28.40  
  Purchase #5 $121.39   4.175%   $126.458   $126.46   $126.45   $126.50  
  Purchase #6 $185.82   8.472%   $201.5627   $201.56   $201.55   $201.60  
  Purchase #7 $176.63   4.493%   $184.566   $184.57   $184.55   $184.60  
  7 purchase totals = $929.86       $995.0725   $995.08   $995.05   $995.10