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 $33.95   5.273%   $35.7402   $35.74   $35.75   $35.70  
  Purchase #2 $108.30   5.205%   $113.937   $113.94   $113.95   $113.90  
  Purchase #3 $27.47   7.558%   $29.5462   $29.55   $29.55   $29.50  
  Purchase #4 $157.70   10.844%   $174.801   $174.80   $174.80   $174.80  
  Purchase #5 $179.49   12.306%   $201.578   $201.58   $201.60   $201.60  
  Purchase #6 $185.99   9.683%   $203.9994   $204.00   $204.00   $204.00  
  Purchase #7 $32.90   12.117%   $36.8865   $36.89   $36.90   $36.90  
  7 purchase totals = $725.80       $796.4883   $796.50   $796.55   $796.40