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 $62.61   11.396%   $69.745   $69.75   $69.75   $69.70  
  Purchase #2 $221.85   13.417%   $251.6156   $251.62   $251.60   $251.60  
  Purchase #3 $111.65   6.377%   $118.7699   $118.77   $118.75   $118.80  
  Purchase #4 $5.26   5.618%   $5.5555   $5.56   $5.55   $5.60  
  Purchase #5 $54.30   12.709%   $61.201   $61.20   $61.20   $61.20  
  Purchase #6 $171.59   8.215%   $185.6861   $185.69   $185.70   $185.70  
  Purchase #7 $247.84   6.507%   $263.9669   $263.97   $263.95   $264.00  
  7 purchase totals = $875.10       $956.5400   $956.56   $956.50   $956.60