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 $98.30   8.525%   $106.6801   $106.68   $106.70   $106.70  
  Purchase #2 $124.25   7.373%   $133.411   $133.41   $133.40   $133.40  
  Purchase #3 $10.76   11.209%   $11.9661   $11.97   $11.95   $12.00  
  Purchase #4 $177.26   5.760%   $187.4702   $187.47   $187.45   $187.50  
  Purchase #5 $190.72   11.292%   $212.2561   $212.26   $212.25   $212.30  
  Purchase #6 $120.42   8.188%   $130.28   $130.28   $130.30   $130.30  
  Purchase #7 $162.55   10.861%   $180.2046   $180.20   $180.20   $180.20  
  7 purchase totals = $884.26       $962.2681   $962.27   $962.25   $962.40