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 $184.79   6.178%   $196.2063   $196.21   $196.20   $196.20  
  Purchase #2 $53.78   9.117%   $58.6831   $58.68   $58.70   $58.70  
  Purchase #3 $59.32   6.825%   $63.3686   $63.37   $63.35   $63.40  
  Purchase #4 $190.89   10.838%   $211.5787   $211.58   $211.60   $211.60  
  Purchase #5 $200.78   5.167%   $211.1543   $211.15   $211.15   $211.20  
  Purchase #6 $58.66   3.539%   $60.736   $60.74   $60.75   $60.70  
  Purchase #7 $191.90   12.358%   $215.615   $215.62   $215.60   $215.60  
  7 purchase totals = $940.12       $1,017.3420   $1,017.35   $1,017.35   $1,017.40