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 $37.86   8.715%   $41.1595   $41.16   $41.15   $41.20  
  Purchase #2 $182.52   13.857%   $207.8118   $207.81   $207.80   $207.80  
  Purchase #3 $172.83   11.127%   $192.0608   $192.06   $192.05   $192.10  
  Purchase #4 $219.69   5.467%   $231.7005   $231.70   $231.70   $231.70  
  Purchase #5 $104.66   9.491%   $114.5933   $114.59   $114.60   $114.60  
  Purchase #6 $151.33   11.571%   $168.8404   $168.84   $168.85   $168.80  
  Purchase #7 $59.85   11.185%   $66.5442   $66.54   $66.55   $66.50  
  7 purchase totals = $928.74       $1,022.7105   $1,022.70   $1,022.70   $1,022.70