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 $59.50   9.356%   $65.0668   $65.07   $65.05   $65.10  
  Purchase #2 $112.62   8.866%   $122.6049   $122.60   $122.60   $122.60  
  Purchase #3 $245.62   7.355%   $263.6854   $263.69   $263.70   $263.70  
  Purchase #4 $217.34   5.589%   $229.4871   $229.49   $229.50   $229.50  
  Purchase #5 $143.56   12.852%   $162.0103   $162.01   $162.00   $162.00  
  Purchase #6 $98.57   4.297%   $102.8056   $102.81   $102.80   $102.80  
  Purchase #7 $83.77   6.134%   $88.9085   $88.91   $88.90   $88.90  
  7 purchase totals = $960.98       $1,034.5686   $1,034.58   $1,034.55   $1,034.60