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 $64.79   10.760%   $71.7614   $71.76   $71.75   $71.80  
  Purchase #2 $188.48   12.380%   $211.8138   $211.81   $211.80   $211.80  
  Purchase #3 $237.83   13.811%   $270.6767   $270.68   $270.70   $270.70  
  Purchase #4 $164.94   10.694%   $182.5787   $182.58   $182.60   $182.60  
  Purchase #5 $134.57   10.157%   $148.2383   $148.24   $148.25   $148.20  
  Purchase #6 $55.27   4.297%   $57.645   $57.65   $57.65   $57.60  
  Purchase #7 $83.96   10.320%   $92.6247   $92.62   $92.60   $92.60  
  7 purchase totals = $929.84       $1,035.3386   $1,035.34   $1,035.35   $1,035.30