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 $182.73   6.390%   $194.4064   $194.41   $194.40   $194.40  
  Purchase #2 $22.48   10.760%   $24.8988   $24.90   $24.90   $24.90  
  Purchase #3 $49.64   9.287%   $54.2501   $54.25   $54.25   $54.30  
  Purchase #4 $190.32   3.279%   $196.5606   $196.56   $196.55   $196.60  
  Purchase #5 $87.38   8.549%   $94.8501   $94.85   $94.85   $94.90  
  Purchase #6 $221.92   5.807%   $234.8069   $234.81   $234.80   $234.80  
  Purchase #7 $208.77   8.346%   $226.1939   $226.19   $226.20   $226.20  
  7 purchase totals = $963.24       $1,025.9668   $1,025.97   $1,025.95   $1,026.10