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 $126.80   5.654%   $133.9693   $133.97   $133.95   $134.00  
  Purchase #2 $197.26   10.643%   $218.2544   $218.25   $218.25   $218.30  
  Purchase #3 $196.37   3.856%   $203.942   $203.94   $203.95   $203.90  
  Purchase #4 $117.35   13.692%   $133.4176   $133.42   $133.40   $133.40  
  Purchase #5 $136.56   13.546%   $155.0584   $155.06   $155.05   $155.10  
  Purchase #6 $248.96   9.281%   $272.066   $272.07   $272.05   $272.10  
  Purchase #7 $40.81   6.276%   $43.3712   $43.37   $43.35   $43.40  
  7 purchase totals = $1,064.11       $1,160.0789   $1,160.08   $1,160.00   $1,160.20