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 $56.43   11.234%   $62.7693   $62.77   $62.75   $62.80  
  Purchase #2 $52.54   4.193%   $54.743   $54.74   $54.75   $54.70  
  Purchase #3 $172.59   10.127%   $190.0682   $190.07   $190.05   $190.10  
  Purchase #4 $183.70   11.501%   $204.8273   $204.83   $204.85   $204.80  
  Purchase #5 $143.91   7.149%   $154.1981   $154.20   $154.20   $154.20  
  Purchase #6 $217.49   3.438%   $224.9673   $224.97   $224.95   $225.00  
  Purchase #7 $246.44   7.395%   $264.6642   $264.66   $264.65   $264.70  
  7 purchase totals = $1,073.10       $1,156.2374   $1,156.24   $1,156.20   $1,156.30