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 $86.94   10.595%   $96.1513   $96.15   $96.15   $96.20  
  Purchase #2 $104.40   8.672%   $113.4536   $113.45   $113.45   $113.50  
  Purchase #3 $163.42   8.688%   $177.6179   $177.62   $177.60   $177.60  
  Purchase #4 $33.25   6.167%   $35.3005   $35.30   $35.30   $35.30  
  Purchase #5 $80.48   5.658%   $85.0336   $85.03   $85.05   $85.00  
  Purchase #6 $121.88   9.755%   $133.7694   $133.77   $133.75   $133.80  
  Purchase #7 $232.95   9.459%   $254.9847   $254.98   $255.00   $255.00  
  7 purchase totals = $823.32       $896.3110   $896.30   $896.30   $896.40