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 $83.81   13.432%   $95.0674   $95.07   $95.05   $95.10  
  Purchase #2 $240.39   7.319%   $257.9841   $257.98   $258.00   $258.00  
  Purchase #3 $232.81   10.752%   $257.8417   $257.84   $257.85   $257.80  
  Purchase #4 $33.47   7.745%   $36.0623   $36.06   $36.05   $36.10  
  Purchase #5 $77.79   9.344%   $85.0587   $85.06   $85.05   $85.10  
  Purchase #6 $246.43   4.497%   $257.512   $257.51   $257.50   $257.50  
  Purchase #7 $32.27   7.295%   $34.6241   $34.62   $34.60   $34.60  
  7 purchase totals = $946.97       $1,024.1503   $1,024.14   $1,024.10   $1,024.20