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 $88.38   8.186%   $95.6148   $95.61   $95.60   $95.60  
  Purchase #2 $190.42   8.635%   $206.8628   $206.86   $206.85   $206.90  
  Purchase #3 $138.66   10.783%   $153.6117   $153.61   $153.60   $153.60  
  Purchase #4 $114.78   8.424%   $124.4491   $124.45   $124.45   $124.40  
  Purchase #5 $201.28   10.361%   $222.1346   $222.13   $222.15   $222.10  
  Purchase #6 $102.94   12.370%   $115.6737   $115.67   $115.65   $115.70  
  Purchase #7 $183.80   11.536%   $205.0032   $205.00   $205.00   $205.00  
  7 purchase totals = $1,020.26       $1,123.3499   $1,123.33   $1,123.30   $1,123.30