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 $239.67   9.352%   $262.0839   $262.08   $262.10   $262.10  
  Purchase #2 $162.73   13.314%   $184.3959   $184.40   $184.40   $184.40  
  Purchase #3 $133.58   8.397%   $144.7967   $144.80   $144.80   $144.80  
  Purchase #4 $76.54   5.359%   $80.6418   $80.64   $80.65   $80.60  
  Purchase #5 $213.93   5.556%   $225.816   $225.82   $225.80   $225.80  
  Purchase #6 $80.33   5.645%   $84.8646   $84.86   $84.85   $84.90  
  Purchase #7 $41.34   12.514%   $46.5133   $46.51   $46.50   $46.50  
  7 purchase totals = $948.12       $1,029.1122   $1,029.11   $1,029.10   $1,029.10