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 $63.83   5.745%   $67.497   $67.50   $67.50   $67.50  
  Purchase #2 $23.32   11.286%   $25.9519   $25.95   $25.95   $26.00  
  Purchase #3 $9.46   13.654%   $10.7517   $10.75   $10.75   $10.80  
  Purchase #4 $49.93   10.715%   $55.28   $55.28   $55.30   $55.30  
  Purchase #5 $180.60   11.440%   $201.2606   $201.26   $201.25   $201.30  
  Purchase #6 $99.33   10.587%   $109.8461   $109.85   $109.85   $109.80  
  Purchase #7 $223.73   5.175%   $235.308   $235.31   $235.30   $235.30  
  7 purchase totals = $650.20       $705.8953   $705.90   $705.90   $706.00