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 $44.43   3.493%   $45.9819   $45.98   $46.00   $46.00  
  Purchase #2 $195.82   8.116%   $211.7128   $211.71   $211.70   $211.70  
  Purchase #3 $124.45   11.668%   $138.9708   $138.97   $138.95   $139.00  
  Purchase #4 $39.95   10.159%   $44.0085   $44.01   $44.00   $44.00  
  Purchase #5 $182.95   7.691%   $197.0207   $197.02   $197.00   $197.00  
  Purchase #6 $164.26   13.508%   $186.4482   $186.45   $186.45   $186.40  
  Purchase #7 $197.98   10.493%   $218.754   $218.75   $218.75   $218.80  
  7 purchase totals = $949.84       $1,042.8969   $1,042.89   $1,042.85   $1,042.90