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 $213.52   10.415%   $235.7581   $235.76   $235.75   $235.80  
  Purchase #2 $247.87   8.466%   $268.8547   $268.85   $268.85   $268.90  
  Purchase #3 $225.46   10.443%   $249.0048   $249.00   $249.00   $249.00  
  Purchase #4 $102.80   11.594%   $114.7186   $114.72   $114.70   $114.70  
  Purchase #5 $215.99   4.404%   $225.5022   $225.50   $225.50   $225.50  
  Purchase #6 $216.89   10.373%   $239.388   $239.39   $239.40   $239.40  
  Purchase #7 $131.27   7.481%   $141.0903   $141.09   $141.10   $141.10  
  7 purchase totals = $1,353.80       $1,474.3167   $1,474.31   $1,474.30   $1,474.40