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 $53.76   7.794%   $57.9501   $57.95   $57.95   $58.00  
  Purchase #2 $147.78   11.459%   $164.7141   $164.71   $164.70   $164.70  
  Purchase #3 $117.31   13.310%   $132.924   $132.92   $132.90   $132.90  
  Purchase #4 $237.26   11.390%   $264.2839   $264.28   $264.30   $264.30  
  Purchase #5 $221.87   6.116%   $235.4396   $235.44   $235.45   $235.40  
  Purchase #6 $58.85   3.245%   $60.7597   $60.76   $60.75   $60.80  
  Purchase #7 $216.98   3.839%   $225.3099   $225.31   $225.30   $225.30  
  7 purchase totals = $1,053.81       $1,141.3813   $1,141.37   $1,141.35   $1,141.40