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 $119.94   5.579%   $126.6315   $126.63   $126.65   $126.60  
  Purchase #2 $135.65   5.414%   $142.9941   $142.99   $143.00   $143.00  
  Purchase #3 $100.32   11.583%   $111.9401   $111.94   $111.95   $111.90  
  Purchase #4 $246.82   7.551%   $265.4574   $265.46   $265.45   $265.50  
  Purchase #5 $101.48   3.165%   $104.6918   $104.69   $104.70   $104.70  
  Purchase #6 $209.45   6.508%   $223.081   $223.08   $223.10   $223.10  
  Purchase #7 $226.45   10.474%   $250.1684   $250.17   $250.15   $250.20  
  7 purchase totals = $1,140.11       $1,224.9643   $1,224.96   $1,225.00   $1,225.00