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 $126.57   11.592%   $141.242   $141.24   $141.25   $141.20  
  Purchase #2 $165.29   10.837%   $183.2025   $183.20   $183.20   $183.20  
  Purchase #3 $42.44   5.672%   $44.8472   $44.85   $44.85   $44.80  
  Purchase #4 $225.25   11.383%   $250.8902   $250.89   $250.90   $250.90  
  Purchase #5 $229.68   10.161%   $253.0178   $253.02   $253.00   $253.00  
  Purchase #6 $174.77   5.591%   $184.5414   $184.54   $184.55   $184.50  
  Purchase #7 $32.31   13.510%   $36.6751   $36.68   $36.70   $36.70  
  7 purchase totals = $996.31       $1,094.4162   $1,094.42   $1,094.45   $1,094.30