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 $106.51   9.140%   $116.245   $116.25   $116.25   $116.20  
  Purchase #2 $237.55   5.702%   $251.0951   $251.10   $251.10   $251.10  
  Purchase #3 $137.83   10.801%   $152.717   $152.72   $152.70   $152.70  
  Purchase #4 $41.90   11.570%   $46.7478   $46.75   $46.75   $46.70  
  Purchase #5 $72.47   11.700%   $80.949   $80.95   $80.95   $80.90  
  Purchase #6 $24.50   7.819%   $26.4157   $26.42   $26.40   $26.40  
  Purchase #7 $73.76   4.516%   $77.091   $77.09   $77.10   $77.10  
  7 purchase totals = $694.52       $751.2606   $751.28   $751.25   $751.10