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 $84.75   13.107%   $95.8582   $95.86   $95.85   $95.90  
  Purchase #2 $139.46   7.583%   $150.0353   $150.04   $150.05   $150.00  
  Purchase #3 $64.87   7.438%   $69.695   $69.70   $69.70   $69.70  
  Purchase #4 $227.73   3.593%   $235.9123   $235.91   $235.90   $235.90  
  Purchase #5 $21.58   11.660%   $24.0962   $24.10   $24.10   $24.10  
  Purchase #6 $38.27   11.547%   $42.689   $42.69   $42.70   $42.70  
  Purchase #7 $122.70   4.143%   $127.7835   $127.78   $127.80   $127.80  
  7 purchase totals = $699.36       $746.0695   $746.08   $746.10   $746.10