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 $96.70   10.602%   $106.9521   $106.95   $106.95   $107.00  
  Purchase #2 $228.79   7.438%   $245.8074   $245.81   $245.80   $245.80  
  Purchase #3 $40.61   4.805%   $42.5613   $42.56   $42.55   $42.60  
  Purchase #4 $219.89   13.634%   $249.8698   $249.87   $249.85   $249.90  
  Purchase #5 $242.26   10.482%   $267.6537   $267.65   $267.65   $267.70  
  Purchase #6 $47.60   3.410%   $49.2232   $49.22   $49.20   $49.20  
  Purchase #7 $96.40   12.217%   $108.1772   $108.18   $108.20   $108.20  
  7 purchase totals = $972.25       $1,070.2447   $1,070.24   $1,070.20   $1,070.40