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 $191.56   5.262%   $201.6399   $201.64   $201.65   $201.60  
  Purchase #2 $136.71   6.581%   $145.7069   $145.71   $145.70   $145.70  
  Purchase #3 $112.70   13.780%   $128.2301   $128.23   $128.25   $128.20  
  Purchase #4 $45.73   13.767%   $52.0256   $52.03   $52.05   $52.00  
  Purchase #5 $70.32   12.668%   $79.2281   $79.23   $79.25   $79.20  
  Purchase #6 $61.33   11.137%   $68.1603   $68.16   $68.15   $68.20  
  Purchase #7 $37.46   5.725%   $39.6046   $39.60   $39.60   $39.60  
  7 purchase totals = $655.81       $714.5955   $714.60   $714.65   $714.50