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 $69.58   3.347%   $71.9088   $71.91   $71.90   $71.90  
  Purchase #2 $43.66   13.382%   $49.5026   $49.50   $49.50   $49.50  
  Purchase #3 $78.79   12.494%   $88.634   $88.63   $88.65   $88.60  
  Purchase #4 $87.26   8.553%   $94.7233   $94.72   $94.70   $94.70  
  Purchase #5 $196.47   7.603%   $211.4076   $211.41   $211.40   $211.40  
  Purchase #6 $155.37   7.158%   $166.4914   $166.49   $166.50   $166.50  
  Purchase #7 $248.26   12.525%   $279.3546   $279.35   $279.35   $279.40  
  7 purchase totals = $879.39       $962.0223   $962.01   $962.00   $962.00