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 $209.46   3.152%   $216.0622   $216.06   $216.05   $216.10  
  Purchase #2 $113.39   9.706%   $124.3956   $124.40   $124.40   $124.40  
  Purchase #3 $169.60   10.104%   $186.7364   $186.74   $186.75   $186.70  
  Purchase #4 $216.90   10.284%   $239.206   $239.21   $239.20   $239.20  
  Purchase #5 $81.46   4.752%   $85.331   $85.33   $85.35   $85.30  
  Purchase #6 $151.53   8.692%   $164.701   $164.70   $164.70   $164.70  
  Purchase #7 $71.69   11.650%   $80.0419   $80.04   $80.05   $80.00  
  7 purchase totals = $1,014.03       $1,096.4741   $1,096.48   $1,096.50   $1,096.40