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 $93.56   11.505%   $104.3241   $104.32   $104.30   $104.30  
  Purchase #2 $188.67   7.849%   $203.4787   $203.48   $203.50   $203.50  
  Purchase #3 $60.61   5.147%   $63.7296   $63.73   $63.75   $63.70  
  Purchase #4 $213.93   8.351%   $231.7953   $231.80   $231.80   $231.80  
  Purchase #5 $222.38   7.198%   $238.3869   $238.39   $238.40   $238.40  
  Purchase #6 $242.34   10.801%   $268.5151   $268.52   $268.50   $268.50  
  Purchase #7 $84.62   13.264%   $95.844   $95.84   $95.85   $95.80  
  7 purchase totals = $1,106.11       $1,206.0737   $1,206.08   $1,206.10   $1,206.00