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 $216.28   3.837%   $224.5787   $224.58   $224.60   $224.60  
  Purchase #2 $193.65   6.245%   $205.7434   $205.74   $205.75   $205.70  
  Purchase #3 $205.39   12.754%   $231.5854   $231.59   $231.60   $231.60  
  Purchase #4 $126.69   12.544%   $142.582   $142.58   $142.60   $142.60  
  Purchase #5 $118.38   3.199%   $122.167   $122.17   $122.15   $122.20  
  Purchase #6 $237.28   6.465%   $252.6202   $252.62   $252.60   $252.60  
  Purchase #7 $17.65   3.592%   $18.284   $18.28   $18.30   $18.30  
  7 purchase totals = $1,115.32       $1,197.5607   $1,197.56   $1,197.60   $1,197.60