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 $12.62   12.366%   $14.1806   $14.18   $14.20   $14.20  
  Purchase #2 $101.34   5.566%   $106.9806   $106.98   $107.00   $107.00  
  Purchase #3 $167.91   9.158%   $183.2872   $183.29   $183.30   $183.30  
  Purchase #4 $243.43   3.662%   $252.3444   $252.34   $252.35   $252.30  
  Purchase #5 $213.34   7.535%   $229.4152   $229.42   $229.40   $229.40  
  Purchase #6 $59.99   8.349%   $64.9986   $65.00   $65.00   $65.00  
  Purchase #7 $222.83   8.356%   $241.4497   $241.45   $241.45   $241.40  
  7 purchase totals = $1,021.46       $1,092.6563   $1,092.66   $1,092.70   $1,092.60