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 $195.33   3.456%   $202.0806   $202.08   $202.10   $202.10  
  Purchase #2 $59.93   3.845%   $62.2343   $62.23   $62.25   $62.20  
  Purchase #3 $186.79   4.435%   $195.0741   $195.07   $195.05   $195.10  
  Purchase #4 $99.90   5.688%   $105.5823   $105.58   $105.60   $105.60  
  Purchase #5 $186.92   5.433%   $197.0754   $197.08   $197.10   $197.10  
  Purchase #6 $222.29   6.856%   $237.5302   $237.53   $237.55   $237.50  
  Purchase #7 $182.72   12.587%   $205.719   $205.72   $205.70   $205.70  
  7 purchase totals = $1,133.88       $1,205.2959   $1,205.29   $1,205.35   $1,205.30