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 $179.77   11.837%   $201.0494   $201.05   $201.05   $201.00  
  Purchase #2 $38.64   11.522%   $43.0921   $43.09   $43.10   $43.10  
  Purchase #3 $247.78   6.859%   $264.7752   $264.78   $264.80   $264.80  
  Purchase #4 $186.92   13.360%   $211.8925   $211.89   $211.90   $211.90  
  Purchase #5 $135.86   13.313%   $153.947   $153.95   $153.95   $153.90  
  Purchase #6 $84.54   12.475%   $95.0864   $95.09   $95.10   $95.10  
  Purchase #7 $59.67   6.143%   $63.3355   $63.34   $63.35   $63.30  
  7 purchase totals = $933.18       $1,033.1781   $1,033.19   $1,033.25   $1,033.10