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 $84.31   10.338%   $93.026   $93.03   $93.05   $93.00  
  Purchase #2 $242.25   3.171%   $249.9317   $249.93   $249.95   $249.90  
  Purchase #3 $124.28   9.158%   $135.6616   $135.66   $135.65   $135.70  
  Purchase #4 $79.54   8.243%   $86.0965   $86.10   $86.10   $86.10  
  Purchase #5 $223.45   7.683%   $240.6177   $240.62   $240.60   $240.60  
  Purchase #6 $81.81   8.398%   $88.6804   $88.68   $88.70   $88.70  
  Purchase #7 $181.73   10.774%   $201.3096   $201.31   $201.30   $201.30  
  7 purchase totals = $1,017.37       $1,095.3235   $1,095.33   $1,095.35   $1,095.30