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 $126.59   6.449%   $134.7538   $134.75   $134.75   $134.80  
  Purchase #2 $198.30   5.579%   $209.3632   $209.36   $209.35   $209.40  
  Purchase #3 $168.77   10.571%   $186.6107   $186.61   $186.60   $186.60  
  Purchase #4 $206.54   11.329%   $229.9389   $229.94   $229.95   $229.90  
  Purchase #5 $59.36   9.153%   $64.7932   $64.79   $64.80   $64.80  
  Purchase #6 $23.27   5.155%   $24.4696   $24.47   $24.45   $24.50  
  Purchase #7 $164.98   12.291%   $185.2577   $185.26   $185.25   $185.30  
  7 purchase totals = $947.81       $1,035.1871   $1,035.18   $1,035.15   $1,035.30