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 $86.61   8.837%   $94.2637   $94.26   $94.25   $94.30  
  Purchase #2 $175.28   9.493%   $191.9193   $191.92   $191.90   $191.90  
  Purchase #3 $53.25   9.237%   $58.1687   $58.17   $58.15   $58.20  
  Purchase #4 $218.66   7.571%   $235.2147   $235.21   $235.20   $235.20  
  Purchase #5 $37.96   3.766%   $39.3896   $39.39   $39.40   $39.40  
  Purchase #6 $220.51   6.418%   $234.6623   $234.66   $234.65   $234.70  
  Purchase #7 $193.82   11.339%   $215.7972   $215.80   $215.80   $215.80  
  7 purchase totals = $986.09       $1,069.4155   $1,069.41   $1,069.35   $1,069.50