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 $161.27   11.459%   $179.7499   $179.75   $179.75   $179.70  
  Purchase #2 $218.47   6.222%   $232.0632   $232.06   $232.05   $232.10  
  Purchase #3 $236.32   11.606%   $263.7473   $263.75   $263.75   $263.70  
  Purchase #4 $191.47   11.295%   $213.0965   $213.10   $213.10   $213.10  
  Purchase #5 $223.65   13.776%   $254.46   $254.46   $254.45   $254.50  
  Purchase #6 $241.53   11.768%   $269.9533   $269.95   $269.95   $270.00  
  Purchase #7 $94.97   11.716%   $106.0967   $106.10   $106.10   $106.10  
  7 purchase totals = $1,367.68       $1,519.1669   $1,519.17   $1,519.15   $1,519.20