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 $67.41   10.727%   $74.6411   $74.64   $74.65   $74.60  
  Purchase #2 $110.39   8.159%   $119.3967   $119.40   $119.40   $119.40  
  Purchase #3 $230.51   12.283%   $258.8235   $258.82   $258.80   $258.80  
  Purchase #4 $231.81   8.748%   $252.0887   $252.09   $252.10   $252.10  
  Purchase #5 $9.33   13.808%   $10.6183   $10.62   $10.60   $10.60  
  Purchase #6 $154.29   7.244%   $165.4668   $165.47   $165.45   $165.50  
  Purchase #7 $66.32   5.475%   $69.951   $69.95   $69.95   $70.00  
  7 purchase totals = $870.06       $950.9861   $950.99   $950.95   $951.00