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 $35.53   3.234%   $36.679   $36.68   $36.70   $36.70  
  Purchase #2 $108.56   4.436%   $113.3757   $113.38   $113.40   $113.40  
  Purchase #3 $211.32   10.416%   $233.3311   $233.33   $233.35   $233.30  
  Purchase #4 $122.43   11.613%   $136.6478   $136.65   $136.65   $136.60  
  Purchase #5 $246.54   4.697%   $258.12   $258.12   $258.10   $258.10  
  Purchase #6 $198.44   6.316%   $210.9735   $210.97   $210.95   $211.00  
  Purchase #7 $63.41   10.429%   $70.023   $70.02   $70.00   $70.00  
  7 purchase totals = $986.23       $1,059.1501   $1,059.15   $1,059.15   $1,059.10