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 $84.61   12.763%   $95.4088   $95.41   $95.40   $95.40  
  Purchase #2 $199.92   4.771%   $209.4582   $209.46   $209.45   $209.50  
  Purchase #3 $210.36   5.530%   $221.9929   $221.99   $222.00   $222.00  
  Purchase #4 $233.53   8.224%   $252.7355   $252.74   $252.75   $252.70  
  Purchase #5 $142.97   8.255%   $154.7722   $154.77   $154.75   $154.80  
  Purchase #6 $118.83   4.118%   $123.7234   $123.72   $123.70   $123.70  
  Purchase #7 $148.44   13.155%   $167.9673   $167.97   $167.95   $168.00  
  7 purchase totals = $1,138.66       $1,226.0583   $1,226.06   $1,226.00   $1,226.10