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 $176.97   13.596%   $201.0308   $201.03   $201.05   $201.00  
  Purchase #2 $166.69   9.681%   $182.8273   $182.83   $182.85   $182.80  
  Purchase #3 $41.66   4.134%   $43.3822   $43.38   $43.40   $43.40  
  Purchase #4 $241.31   9.321%   $263.8025   $263.80   $263.80   $263.80  
  Purchase #5 $188.33   11.562%   $210.1047   $210.10   $210.10   $210.10  
  Purchase #6 $25.99   3.318%   $26.8523   $26.85   $26.85   $26.90  
  Purchase #7 $81.70   8.550%   $88.6854   $88.69   $88.70   $88.70  
  7 purchase totals = $922.65       $1,016.6852   $1,016.68   $1,016.75   $1,016.70