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 $112.94   11.220%   $125.6119   $125.61   $125.60   $125.60  
  Purchase #2 $247.81   7.282%   $265.8555   $265.86   $265.85   $265.90  
  Purchase #3 $114.86   8.166%   $124.2395   $124.24   $124.25   $124.20  
  Purchase #4 $217.99   7.727%   $234.8341   $234.83   $234.85   $234.80  
  Purchase #5 $242.99   8.327%   $263.2238   $263.22   $263.20   $263.20  
  Purchase #6 $202.79   12.116%   $227.36   $227.36   $227.35   $227.40  
  Purchase #7 $172.40   12.556%   $194.0465   $194.05   $194.05   $194.00  
  7 purchase totals = $1,311.78       $1,435.1713   $1,435.17   $1,435.15   $1,435.10