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 $187.93   9.699%   $206.1573   $206.16   $206.15   $206.20  
  Purchase #2 $181.87   8.282%   $196.9325   $196.93   $196.95   $196.90  
  Purchase #3 $203.36   7.658%   $218.9333   $218.93   $218.95   $218.90  
  Purchase #4 $217.74   5.197%   $229.0559   $229.06   $229.05   $229.10  
  Purchase #5 $246.85   6.539%   $262.9915   $262.99   $263.00   $263.00  
  Purchase #6 $7.34   10.158%   $8.0856   $8.09   $8.10   $8.10  
  Purchase #7 $227.30   8.185%   $245.9045   $245.90   $245.90   $245.90  
  7 purchase totals = $1,272.39       $1,368.0606   $1,368.06   $1,368.10   $1,368.10