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 $84.81   12.560%   $95.4621   $95.46   $95.45   $95.50  
  Purchase #2 $216.39   9.174%   $236.2416   $236.24   $236.25   $236.20  
  Purchase #3 $32.37   11.217%   $36.0009   $36.00   $36.00   $36.00  
  Purchase #4 $179.29   8.130%   $193.8663   $193.87   $193.85   $193.90  
  Purchase #5 $172.46   13.260%   $195.3282   $195.33   $195.35   $195.30  
  Purchase #6 $75.63   6.159%   $80.2881   $80.29   $80.30   $80.30  
  Purchase #7 $215.45   3.229%   $222.4069   $222.41   $222.40   $222.40  
  7 purchase totals = $976.40       $1,059.5941   $1,059.60   $1,059.60   $1,059.60