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 $195.60   3.127%   $201.7164   $201.72   $201.70   $201.70  
  Purchase #2 $61.39   12.872%   $69.2921   $69.29   $69.30   $69.30  
  Purchase #3 $94.75   3.313%   $97.8891   $97.89   $97.90   $97.90  
  Purchase #4 $208.64   7.732%   $224.772   $224.77   $224.75   $224.80  
  Purchase #5 $193.29   3.829%   $200.6911   $200.69   $200.70   $200.70  
  Purchase #6 $36.71   10.406%   $40.53   $40.53   $40.55   $40.50  
  Purchase #7 $152.37   12.136%   $170.8616   $170.86   $170.85   $170.90  
  7 purchase totals = $942.75       $1,005.7523   $1,005.75   $1,005.75   $1,005.80