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 $49.39   13.267%   $55.9426   $55.94   $55.95   $55.90  
  Purchase #2 $172.81   13.229%   $195.671   $195.67   $195.65   $195.70  
  Purchase #3 $105.93   10.195%   $116.7296   $116.73   $116.75   $116.70  
  Purchase #4 $226.85   3.503%   $234.7966   $234.80   $234.80   $234.80  
  Purchase #5 $162.50   3.336%   $167.921   $167.92   $167.90   $167.90  
  Purchase #6 $69.43   13.379%   $78.719   $78.72   $78.70   $78.70  
  Purchase #7 $186.78   4.239%   $194.6976   $194.70   $194.70   $194.70  
  7 purchase totals = $973.69       $1,044.4774   $1,044.48   $1,044.45   $1,044.40