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 $96.61   11.119%   $107.3521   $107.35   $107.35   $107.40  
  Purchase #2 $228.67   8.471%   $248.0406   $248.04   $248.05   $248.00  
  Purchase #3 $81.71   6.113%   $86.7049   $86.70   $86.70   $86.70  
  Purchase #4 $173.55   5.846%   $183.6957   $183.70   $183.70   $183.70  
  Purchase #5 $94.65   7.325%   $101.5831   $101.58   $101.60   $101.60  
  Purchase #6 $137.74   8.371%   $149.2702   $149.27   $149.25   $149.30  
  Purchase #7 $201.91   11.515%   $225.1599   $225.16   $225.15   $225.20  
  7 purchase totals = $1,014.84       $1,101.8065   $1,101.80   $1,101.80   $1,101.90