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 $83.85   13.445%   $95.1236   $95.12   $95.10   $95.10  
  Purchase #2 $193.58   6.123%   $205.4329   $205.43   $205.45   $205.40  
  Purchase #3 $170.41   3.692%   $176.7015   $176.70   $176.70   $176.70  
  Purchase #4 $86.81   11.607%   $96.886   $96.89   $96.90   $96.90  
  Purchase #5 $125.35   9.457%   $137.2043   $137.20   $137.20   $137.20  
  Purchase #6 $104.49   8.381%   $113.2473   $113.25   $113.25   $113.20  
  Purchase #7 $191.67   4.502%   $200.299   $200.30   $200.30   $200.30  
  7 purchase totals = $956.16       $1,024.8946   $1,024.89   $1,024.90   $1,024.80