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 $84.59   12.699%   $95.3321   $95.33   $95.35   $95.30  
  Purchase #2 $82.94   13.282%   $93.9561   $93.96   $93.95   $94.00  
  Purchase #3 $202.45   3.783%   $210.1087   $210.11   $210.10   $210.10  
  Purchase #4 $11.56   13.520%   $13.1229   $13.12   $13.10   $13.10  
  Purchase #5 $29.54   5.856%   $31.2699   $31.27   $31.25   $31.30  
  Purchase #6 $223.60   10.789%   $247.7242   $247.72   $247.70   $247.70  
  Purchase #7 $208.55   11.780%   $233.1172   $233.12   $233.10   $233.10  
  7 purchase totals = $843.23       $924.6311   $924.63   $924.55   $924.60