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 $12.89   8.735%   $14.0159   $14.02   $14.00   $14.00  
  Purchase #2 $157.56   5.454%   $166.1533   $166.15   $166.15   $166.20  
  Purchase #3 $226.45   6.737%   $241.7059   $241.71   $241.70   $241.70  
  Purchase #4 $187.60   4.524%   $196.087   $196.09   $196.10   $196.10  
  Purchase #5 $181.67   11.114%   $201.8608   $201.86   $201.85   $201.90  
  Purchase #6 $200.95   6.305%   $213.6199   $213.62   $213.60   $213.60  
  Purchase #7 $64.35   10.755%   $71.2708   $71.27   $71.25   $71.30  
  7 purchase totals = $1,031.47       $1,104.7136   $1,104.72   $1,104.65   $1,104.80