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 $84.85   11.246%   $94.3922   $94.39   $94.40   $94.40  
  Purchase #2 $224.57   13.576%   $255.0576   $255.06   $255.05   $255.10  
  Purchase #3 $84.82   7.634%   $91.2952   $91.30   $91.30   $91.30  
  Purchase #4 $23.40   6.693%   $24.9662   $24.97   $24.95   $25.00  
  Purchase #5 $150.62   9.190%   $164.462   $164.46   $164.45   $164.50  
  Purchase #6 $24.84   6.429%   $26.437   $26.44   $26.45   $26.40  
  Purchase #7 $99.47   5.713%   $105.1527   $105.15   $105.15   $105.20  
  7 purchase totals = $692.57       $761.7629   $761.77   $761.75   $761.90