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 $241.72   10.337%   $266.7066   $266.71   $266.70   $266.70  
  Purchase #2 $245.26   9.351%   $268.1943   $268.19   $268.20   $268.20  
  Purchase #3 $59.75   9.739%   $65.5691   $65.57   $65.55   $65.60  
  Purchase #4 $232.82   10.545%   $257.3709   $257.37   $257.35   $257.40  
  Purchase #5 $52.76   3.584%   $54.6509   $54.65   $54.65   $54.70  
  Purchase #6 $174.45   11.192%   $193.9744   $193.97   $193.95   $194.00  
  Purchase #7 $41.92   12.146%   $47.0116   $47.01   $47.00   $47.00  
  7 purchase totals = $1,048.68       $1,153.4778   $1,153.47   $1,153.40   $1,153.60