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 $196.98   7.771%   $212.2873   $212.29   $212.30   $212.30  
  Purchase #2 $239.89   9.589%   $262.8931   $262.89   $262.90   $262.90  
  Purchase #3 $75.52   9.613%   $82.7797   $82.78   $82.80   $82.80  
  Purchase #4 $23.44   3.746%   $24.3181   $24.32   $24.30   $24.30  
  Purchase #5 $192.44   7.780%   $207.4118   $207.41   $207.40   $207.40  
  Purchase #6 $123.58   6.541%   $131.6634   $131.66   $131.65   $131.70  
  Purchase #7 $174.70   9.158%   $190.699   $190.70   $190.70   $190.70  
  7 purchase totals = $1,026.55       $1,112.0524   $1,112.05   $1,112.05   $1,112.10