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 $233.61   13.743%   $265.715   $265.72   $265.70   $265.70  
  Purchase #2 $136.84   7.181%   $146.6665   $146.67   $146.65   $146.70  
  Purchase #3 $215.28   13.724%   $244.825   $244.83   $244.85   $244.80  
  Purchase #4 $152.33   6.425%   $162.1172   $162.12   $162.10   $162.10  
  Purchase #5 $48.78   3.640%   $50.5556   $50.56   $50.55   $50.60  
  Purchase #6 $167.46   5.536%   $176.7306   $176.73   $176.75   $176.70  
  Purchase #7 $108.37   6.523%   $115.439   $115.44   $115.45   $115.40  
  7 purchase totals = $1,062.67       $1,162.0489   $1,162.07   $1,162.05   $1,162.00