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 $162.39   8.317%   $175.896   $175.90   $175.90   $175.90  
  Purchase #2 $58.98   7.481%   $63.3923   $63.39   $63.40   $63.40  
  Purchase #3 $83.58   6.195%   $88.7578   $88.76   $88.75   $88.80  
  Purchase #4 $69.94   12.213%   $78.4818   $78.48   $78.50   $78.50  
  Purchase #5 $73.50   7.528%   $79.0331   $79.03   $79.05   $79.00  
  Purchase #6 $91.78   7.131%   $98.3248   $98.32   $98.30   $98.30  
  Purchase #7 $212.38   13.516%   $241.0853   $241.09   $241.10   $241.10  
  7 purchase totals = $752.55       $824.9711   $824.97   $825.00   $825.00