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 $44.84   5.536%   $47.3223   $47.32   $47.30   $47.30  
  Purchase #2 $240.67   5.718%   $254.4315   $254.43   $254.45   $254.40  
  Purchase #3 $169.75   4.348%   $177.1307   $177.13   $177.15   $177.10  
  Purchase #4 $220.55   12.696%   $248.551   $248.55   $248.55   $248.60  
  Purchase #5 $192.56   6.838%   $205.7273   $205.73   $205.75   $205.70  
  Purchase #6 $120.93   13.846%   $137.674   $137.67   $137.65   $137.70  
  Purchase #7 $211.75   12.801%   $238.8561   $238.86   $238.85   $238.90  
  7 purchase totals = $1,201.05       $1,309.6929   $1,309.69   $1,309.70   $1,309.70