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 $222.83   8.267%   $241.2514   $241.25   $241.25   $241.30  
  Purchase #2 $208.99   13.257%   $236.6958   $236.70   $236.70   $236.70  
  Purchase #3 $62.41   10.681%   $69.076   $69.08   $69.10   $69.10  
  Purchase #4 $28.26   11.858%   $31.6111   $31.61   $31.60   $31.60  
  Purchase #5 $242.50   4.348%   $253.0439   $253.04   $253.05   $253.00  
  Purchase #6 $154.69   10.355%   $170.7081   $170.71   $170.70   $170.70  
  Purchase #7 $133.52   13.576%   $151.6467   $151.65   $151.65   $151.60  
  7 purchase totals = $1,053.20       $1,154.0330   $1,154.04   $1,154.05   $1,154.00