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 $68.29   11.300%   $76.0068   $76.01   $76.00   $76.00  
  Purchase #2 $166.88   9.801%   $183.2359   $183.24   $183.25   $183.20  
  Purchase #3 $141.98   8.354%   $153.841   $153.84   $153.85   $153.80  
  Purchase #4 $171.58   4.327%   $179.0043   $179.00   $179.00   $179.00  
  Purchase #5 $198.88   10.137%   $219.0405   $219.04   $219.05   $219.00  
  Purchase #6 $212.48   6.862%   $227.0604   $227.06   $227.05   $227.10  
  Purchase #7 $190.96   13.563%   $216.8599   $216.86   $216.85   $216.90  
  7 purchase totals = $1,151.05       $1,255.0488   $1,255.05   $1,255.05   $1,255.00