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 $97.49   7.527%   $104.8281   $104.83   $104.85   $104.80  
  Purchase #2 $250.48   4.833%   $262.5857   $262.59   $262.60   $262.60  
  Purchase #3 $10.55   8.413%   $11.4376   $11.44   $11.45   $11.40  
  Purchase #4 $120.85   3.665%   $125.2792   $125.28   $125.30   $125.30  
  Purchase #5 $217.52   13.652%   $247.2158   $247.22   $247.20   $247.20  
  Purchase #6 $132.29   12.329%   $148.6   $148.60   $148.60   $148.60  
  Purchase #7 $167.46   4.229%   $174.5419   $174.54   $174.55   $174.50  
  7 purchase totals = $996.64       $1,074.4883   $1,074.50   $1,074.55   $1,074.40