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 $195.62   5.664%   $206.6999   $206.70   $206.70   $206.70  
  Purchase #2 $96.33   10.391%   $106.3397   $106.34   $106.35   $106.30  
  Purchase #3 $28.68   12.366%   $32.2266   $32.23   $32.25   $32.20  
  Purchase #4 $52.61   8.628%   $57.1492   $57.15   $57.15   $57.10  
  Purchase #5 $30.46   11.869%   $34.0753   $34.08   $34.10   $34.10  
  Purchase #6 $118.41   6.529%   $126.141   $126.14   $126.15   $126.10  
  Purchase #7 $134.93   6.183%   $143.2727   $143.27   $143.25   $143.30  
  7 purchase totals = $657.04       $705.9044   $705.91   $705.95   $705.80