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 $59.71   4.572%   $62.4399   $62.44   $62.45   $62.40  
  Purchase #2 $201.61   4.646%   $210.9768   $210.98   $211.00   $211.00  
  Purchase #3 $7.42   7.141%   $7.9499   $7.95   $7.95   $7.90  
  Purchase #4 $84.93   12.816%   $95.8146   $95.81   $95.80   $95.80  
  Purchase #5 $210.96   8.277%   $228.4212   $228.42   $228.40   $228.40  
  Purchase #6 $159.25   10.355%   $175.7403   $175.74   $175.75   $175.70  
  Purchase #7 $69.61   8.260%   $75.3598   $75.36   $75.35   $75.40  
  7 purchase totals = $793.49       $856.7025   $856.70   $856.70   $856.60