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 $85.45   11.225%   $95.0418   $95.04   $95.05   $95.00  
  Purchase #2 $235.83   11.230%   $262.3137   $262.31   $262.30   $262.30  
  Purchase #3 $143.93   12.469%   $161.8766   $161.88   $161.90   $161.90  
  Purchase #4 $36.52   3.535%   $37.811   $37.81   $37.80   $37.80  
  Purchase #5 $179.26   13.335%   $203.1643   $203.16   $203.15   $203.20  
  Purchase #6 $180.68   7.672%   $194.5418   $194.54   $194.55   $194.50  
  Purchase #7 $120.63   12.850%   $136.131   $136.13   $136.15   $136.10  
  7 purchase totals = $982.30       $1,090.8802   $1,090.87   $1,090.90   $1,090.80