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 $126.66   11.463%   $141.179   $141.18   $141.20   $141.20  
  Purchase #2 $238.42   3.169%   $245.9755   $245.98   $246.00   $246.00  
  Purchase #3 $221.40   4.723%   $231.8567   $231.86   $231.85   $231.90  
  Purchase #4 $114.25   9.238%   $124.8044   $124.80   $124.80   $124.80  
  Purchase #5 $58.28   3.170%   $60.1275   $60.13   $60.15   $60.10  
  Purchase #6 $179.58   9.402%   $196.4641   $196.46   $196.45   $196.50  
  Purchase #7 $249.36   12.701%   $281.0312   $281.03   $281.05   $281.00  
  7 purchase totals = $1,187.95       $1,281.4384   $1,281.44   $1,281.50   $1,281.50