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 $60.28   6.633%   $64.2784   $64.28   $64.30   $64.30  
  Purchase #2 $23.72   4.362%   $24.7547   $24.75   $24.75   $24.80  
  Purchase #3 $247.75   7.661%   $266.7301   $266.73   $266.75   $266.70  
  Purchase #4 $228.26   3.609%   $236.4979   $236.50   $236.50   $236.50  
  Purchase #5 $89.71   4.715%   $93.9398   $93.94   $93.95   $93.90  
  Purchase #6 $194.86   11.213%   $216.7097   $216.71   $216.70   $216.70  
  Purchase #7 $167.63   3.591%   $173.6496   $173.65   $173.65   $173.60  
  7 purchase totals = $1,012.21       $1,076.5602   $1,076.56   $1,076.60   $1,076.50