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 $232.96   3.841%   $241.908   $241.91   $241.90   $241.90  
  Purchase #2 $14.46   6.160%   $15.3507   $15.35   $15.35   $15.40  
  Purchase #3 $211.82   11.306%   $235.7684   $235.77   $235.75   $235.80  
  Purchase #4 $233.35   5.806%   $246.8983   $246.90   $246.90   $246.90  
  Purchase #5 $227.71   4.420%   $237.7748   $237.77   $237.75   $237.80  
  Purchase #6 $237.89   9.167%   $259.6974   $259.70   $259.70   $259.70  
  Purchase #7 $174.90   3.693%   $181.3591   $181.36   $181.35   $181.40  
  7 purchase totals = $1,333.09       $1,418.7567   $1,418.76   $1,418.70   $1,418.90