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 $114.58   10.259%   $126.3348   $126.33   $126.35   $126.30  
  Purchase #2 $177.25   13.174%   $200.6009   $200.60   $200.60   $200.60  
  Purchase #3 $173.93   13.826%   $197.9776   $197.98   $198.00   $198.00  
  Purchase #4 $14.70   13.186%   $16.6383   $16.64   $16.65   $16.60  
  Purchase #5 $236.89   11.773%   $264.7791   $264.78   $264.80   $264.80  
  Purchase #6 $235.89   12.491%   $265.355   $265.36   $265.35   $265.40  
  Purchase #7 $157.54   7.822%   $169.8628   $169.86   $169.85   $169.90  
  7 purchase totals = $1,110.78       $1,241.5485   $1,241.55   $1,241.60   $1,241.60