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 $163.39   7.412%   $175.5005   $175.50   $175.50   $175.50  
  Purchase #2 $75.86   6.385%   $80.7037   $80.70   $80.70   $80.70  
  Purchase #3 $99.94   10.534%   $110.4677   $110.47   $110.45   $110.50  
  Purchase #4 $150.95   3.797%   $156.6816   $156.68   $156.70   $156.70  
  Purchase #5 $208.60   12.739%   $235.1736   $235.17   $235.15   $235.20  
  Purchase #6 $245.58   10.725%   $271.9185   $271.92   $271.90   $271.90  
  Purchase #7 $161.47   9.757%   $177.2246   $177.22   $177.20   $177.20  
  7 purchase totals = $1,105.79       $1,207.6702   $1,207.66   $1,207.60   $1,207.70