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 $76.35   8.221%   $82.6267   $82.63   $82.65   $82.60  
  Purchase #2 $232.45   6.212%   $246.8898   $246.89   $246.90   $246.90  
  Purchase #3 $77.73   9.581%   $85.1773   $85.18   $85.20   $85.20  
  Purchase #4 $165.69   5.292%   $174.4583   $174.46   $174.45   $174.50  
  Purchase #5 $186.67   7.792%   $201.2153   $201.22   $201.20   $201.20  
  Purchase #6 $116.98   9.779%   $128.4195   $128.42   $128.40   $128.40  
  Purchase #7 $118.97   8.544%   $129.1348   $129.13   $129.15   $129.10  
  7 purchase totals = $974.84       $1,047.9217   $1,047.93   $1,047.95   $1,047.90