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 $35.98   5.871%   $38.0924   $38.09   $38.10   $38.10  
  Purchase #2 $182.62   8.114%   $197.4378   $197.44   $197.45   $197.40  
  Purchase #3 $71.69   7.562%   $77.1112   $77.11   $77.10   $77.10  
  Purchase #4 $157.70   12.181%   $176.9094   $176.91   $176.90   $176.90  
  Purchase #5 $145.81   8.667%   $158.4474   $158.45   $158.45   $158.40  
  Purchase #6 $202.72   10.366%   $223.734   $223.73   $223.75   $223.70  
  Purchase #7 $171.81   11.799%   $192.0819   $192.08   $192.10   $192.10  
  7 purchase totals = $968.33       $1,063.8141   $1,063.81   $1,063.85   $1,063.70