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 $65.87   4.770%   $69.012   $69.01   $69.00   $69.00  
  Purchase #2 $166.29   3.769%   $172.5575   $172.56   $172.55   $172.60  
  Purchase #3 $239.99   12.468%   $269.912   $269.91   $269.90   $269.90  
  Purchase #4 $205.76   3.282%   $212.513   $212.51   $212.50   $212.50  
  Purchase #5 $180.80   5.514%   $190.7693   $190.77   $190.75   $190.80  
  Purchase #6 $215.71   11.554%   $240.6331   $240.63   $240.65   $240.60  
  Purchase #7 $190.72   6.715%   $203.5268   $203.53   $203.55   $203.50  
  7 purchase totals = $1,265.14       $1,358.9237   $1,358.92   $1,358.90   $1,358.90