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 $62.76   8.458%   $68.0682   $68.07   $68.05   $68.10  
  Purchase #2 $209.36   7.311%   $224.6663   $224.67   $224.65   $224.70  
  Purchase #3 $102.25   10.199%   $112.6785   $112.68   $112.70   $112.70  
  Purchase #4 $148.98   12.109%   $167.02   $167.02   $167.00   $167.00  
  Purchase #5 $214.44   10.262%   $236.4458   $236.45   $236.45   $236.40  
  Purchase #6 $46.96   12.553%   $52.8549   $52.85   $52.85   $52.90  
  Purchase #7 $147.69   10.508%   $163.2093   $163.21   $163.20   $163.20  
  7 purchase totals = $932.44       $1,024.9430   $1,024.95   $1,024.90   $1,025.00