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 $204.86   10.161%   $225.6758   $225.68   $225.70   $225.70  
  Purchase #2 $165.25   13.531%   $187.61   $187.61   $187.60   $187.60  
  Purchase #3 $151.66   7.650%   $163.262   $163.26   $163.25   $163.30  
  Purchase #4 $157.97   13.657%   $179.544   $179.54   $179.55   $179.50  
  Purchase #5 $64.39   13.451%   $73.0511   $73.05   $73.05   $73.10  
  Purchase #6 $136.45   12.552%   $153.5772   $153.58   $153.60   $153.60  
  Purchase #7 $202.51   8.685%   $220.098   $220.10   $220.10   $220.10  
  7 purchase totals = $1,083.09       $1,202.8181   $1,202.82   $1,202.85   $1,202.90