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 $41.50   5.213%   $43.6634   $43.66   $43.65   $43.70  
  Purchase #2 $171.80   13.764%   $195.4466   $195.45   $195.45   $195.40  
  Purchase #3 $60.41   3.423%   $62.4778   $62.48   $62.50   $62.50  
  Purchase #4 $167.63   10.330%   $184.9462   $184.95   $184.95   $184.90  
  Purchase #5 $26.95   4.191%   $28.0795   $28.08   $28.10   $28.10  
  Purchase #6 $182.73   8.464%   $198.1963   $198.20   $198.20   $198.20  
  Purchase #7 $23.99   3.576%   $24.8479   $24.85   $24.85   $24.80  
  7 purchase totals = $675.01       $737.6577   $737.67   $737.70   $737.60