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 $32.82   3.492%   $33.9661   $33.97   $33.95   $34.00  
  Purchase #2 $119.33   12.864%   $134.6806   $134.68   $134.70   $134.70  
  Purchase #3 $106.25   13.178%   $120.2516   $120.25   $120.25   $120.30  
  Purchase #4 $217.61   4.858%   $228.1815   $228.18   $228.20   $228.20  
  Purchase #5 $201.46   13.492%   $228.641   $228.64   $228.65   $228.60  
  Purchase #6 $122.25   3.425%   $126.4371   $126.44   $126.45   $126.40  
  Purchase #7 $187.51   5.817%   $198.4175   $198.42   $198.40   $198.40  
  7 purchase totals = $987.23       $1,070.5754   $1,070.58   $1,070.60   $1,070.60