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 $205.41   13.675%   $233.4998   $233.50   $233.50   $233.50  
  Purchase #2 $227.91   10.262%   $251.2981   $251.30   $251.30   $251.30  
  Purchase #3 $35.70   13.871%   $40.6519   $40.65   $40.65   $40.70  
  Purchase #4 $36.97   10.461%   $40.8374   $40.84   $40.85   $40.80  
  Purchase #5 $228.30   10.700%   $252.7281   $252.73   $252.75   $252.70  
  Purchase #6 $10.69   5.326%   $11.2593   $11.26   $11.25   $11.30  
  Purchase #7 $209.94   8.507%   $227.7996   $227.80   $227.80   $227.80  
  7 purchase totals = $954.92       $1,058.0742   $1,058.08   $1,058.10   $1,058.10