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 $68.45   4.637%   $71.624   $71.62   $71.60   $71.60  
  Purchase #2 $203.27   9.566%   $222.7148   $222.71   $222.70   $222.70  
  Purchase #3 $15.56   12.336%   $17.4795   $17.48   $17.50   $17.50  
  Purchase #4 $176.82   9.265%   $193.2024   $193.20   $193.20   $193.20  
  Purchase #5 $86.56   4.731%   $90.6552   $90.66   $90.65   $90.70  
  Purchase #6 $89.65   6.178%   $95.1886   $95.19   $95.20   $95.20  
  Purchase #7 $67.79   3.446%   $70.126   $70.13   $70.15   $70.10  
  7 purchase totals = $708.10       $760.9905   $760.99   $761.00   $761.00