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 $92.63   10.843%   $102.6739   $102.67   $102.65   $102.70  
  Purchase #2 $166.39   12.824%   $187.7279   $187.73   $187.75   $187.70  
  Purchase #3 $179.63   4.853%   $188.3474   $188.35   $188.35   $188.30  
  Purchase #4 $157.36   5.194%   $165.5333   $165.53   $165.55   $165.50  
  Purchase #5 $190.78   10.868%   $211.514   $211.51   $211.50   $211.50  
  Purchase #6 $39.61   10.874%   $43.9172   $43.92   $43.90   $43.90  
  Purchase #7 $107.28   12.626%   $120.8252   $120.83   $120.85   $120.80  
  7 purchase totals = $933.68       $1,020.5389   $1,020.54   $1,020.55   $1,020.40