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 $57.58   8.621%   $62.544   $62.54   $62.55   $62.50  
  Purchase #2 $114.89   3.267%   $118.6435   $118.64   $118.65   $118.60  
  Purchase #3 $249.91   8.435%   $270.9899   $270.99   $271.00   $271.00  
  Purchase #4 $168.65   3.567%   $174.6657   $174.67   $174.65   $174.70  
  Purchase #5 $99.68   6.776%   $106.4343   $106.43   $106.45   $106.40  
  Purchase #6 $115.63   9.646%   $126.7837   $126.78   $126.80   $126.80  
  Purchase #7 $89.99   3.384%   $93.0353   $93.04   $93.05   $93.00  
  7 purchase totals = $896.33       $953.0964   $953.09   $953.15   $953.00