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 $54.59   13.475%   $61.946   $61.95   $61.95   $61.90  
  Purchase #2 $249.92   13.333%   $283.2418   $283.24   $283.25   $283.20  
  Purchase #3 $130.97   13.860%   $149.1224   $149.12   $149.10   $149.10  
  Purchase #4 $201.39   12.715%   $226.9967   $227.00   $227.00   $227.00  
  Purchase #5 $40.54   10.352%   $44.7367   $44.74   $44.75   $44.70  
  Purchase #6 $139.73   10.526%   $154.438   $154.44   $154.45   $154.40  
  Purchase #7 $84.92   3.375%   $87.7861   $87.79   $87.80   $87.80  
  7 purchase totals = $902.06       $1,008.2677   $1,008.28   $1,008.30   $1,008.10