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 $194.97   5.767%   $206.2139   $206.21   $206.20   $206.20  
  Purchase #2 $60.25   11.481%   $67.1673   $67.17   $67.15   $67.20  
  Purchase #3 $68.81   8.480%   $74.6451   $74.65   $74.65   $74.60  
  Purchase #4 $34.71   7.847%   $37.4337   $37.43   $37.45   $37.40  
  Purchase #5 $23.90   13.311%   $27.0813   $27.08   $27.10   $27.10  
  Purchase #6 $90.50   3.874%   $94.006   $94.01   $94.00   $94.00  
  Purchase #7 $114.63   3.365%   $118.4873   $118.49   $118.50   $118.50  
  7 purchase totals = $587.77       $625.0346   $625.04   $625.05   $625.00