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 $195.66   7.211%   $209.769   $209.77   $209.75   $209.80  
  Purchase #2 $21.39   10.443%   $23.6238   $23.62   $23.60   $23.60  
  Purchase #3 $168.96   10.281%   $186.3308   $186.33   $186.35   $186.30  
  Purchase #4 $66.94   10.815%   $74.1796   $74.18   $74.20   $74.20  
  Purchase #5 $211.68   11.724%   $236.4974   $236.50   $236.50   $236.50  
  Purchase #6 $207.52   3.555%   $214.8973   $214.90   $214.90   $214.90  
  Purchase #7 $208.87   8.213%   $226.0245   $226.02   $226.00   $226.00  
  7 purchase totals = $1,081.02       $1,171.3224   $1,171.32   $1,171.30   $1,171.30