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 $89.58   5.242%   $94.2758   $94.28   $94.30   $94.30  
  Purchase #2 $197.66   9.631%   $216.6966   $216.70   $216.70   $216.70  
  Purchase #3 $24.47   10.709%   $27.0905   $27.09   $27.10   $27.10  
  Purchase #4 $31.93   5.337%   $33.6341   $33.63   $33.65   $33.60  
  Purchase #5 $90.65   5.270%   $95.4273   $95.43   $95.45   $95.40  
  Purchase #6 $179.92   10.394%   $198.6209   $198.62   $198.60   $198.60  
  Purchase #7 $129.59   7.185%   $138.901   $138.90   $138.90   $138.90  
  7 purchase totals = $743.80       $804.6462   $804.65   $804.70   $804.60