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 $119.75   4.497%   $125.1352   $125.14   $125.15   $125.10  
  Purchase #2 $52.71   4.783%   $55.2311   $55.23   $55.25   $55.20  
  Purchase #3 $226.34   9.590%   $248.046   $248.05   $248.05   $248.00  
  Purchase #4 $10.83   7.492%   $11.6414   $11.64   $11.65   $11.60  
  Purchase #5 $223.88   11.298%   $249.174   $249.17   $249.15   $249.20  
  Purchase #6 $106.25   10.114%   $116.9961   $117.00   $117.00   $117.00  
  Purchase #7 $203.50   9.604%   $223.0441   $223.04   $223.05   $223.00  
  7 purchase totals = $943.26       $1,029.2679   $1,029.27   $1,029.30   $1,029.10