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 $215.97   8.161%   $233.5953   $233.60   $233.60   $233.60  
  Purchase #2 $74.30   12.603%   $83.664   $83.66   $83.65   $83.70  
  Purchase #3 $69.89   8.413%   $75.7698   $75.77   $75.75   $75.80  
  Purchase #4 $154.53   11.335%   $172.046   $172.05   $172.05   $172.00  
  Purchase #5 $99.93   6.586%   $106.5114   $106.51   $106.50   $106.50  
  Purchase #6 $171.70   7.459%   $184.5071   $184.51   $184.50   $184.50  
  Purchase #7 $41.72   8.514%   $45.272   $45.27   $45.25   $45.30  
  7 purchase totals = $828.04       $901.3656   $901.37   $901.30   $901.40