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 $104.52   9.702%   $114.6605   $114.66   $114.65   $114.70  
  Purchase #2 $61.87   13.865%   $70.4483   $70.45   $70.45   $70.40  
  Purchase #3 $146.55   3.722%   $152.0046   $152.00   $152.00   $152.00  
  Purchase #4 $38.62   5.648%   $40.8013   $40.80   $40.80   $40.80  
  Purchase #5 $154.67   9.648%   $169.5926   $169.59   $169.60   $169.60  
  Purchase #6 $172.69   10.566%   $190.9364   $190.94   $190.95   $190.90  
  Purchase #7 $16.52   5.370%   $17.4071   $17.41   $17.40   $17.40  
  7 purchase totals = $695.44       $755.8508   $755.85   $755.85   $755.80