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 $201.48   3.209%   $207.9455   $207.95   $207.95   $207.90  
  Purchase #2 $220.47   9.339%   $241.0597   $241.06   $241.05   $241.10  
  Purchase #3 $27.55   6.385%   $29.3091   $29.31   $29.30   $29.30  
  Purchase #4 $93.66   7.661%   $100.8353   $100.84   $100.85   $100.80  
  Purchase #5 $167.51   4.818%   $175.5806   $175.58   $175.60   $175.60  
  Purchase #6 $176.37   4.496%   $184.2996   $184.30   $184.30   $184.30  
  Purchase #7 $163.63   6.372%   $174.0565   $174.06   $174.05   $174.10  
  7 purchase totals = $1,050.67       $1,113.0863   $1,113.10   $1,113.10   $1,113.10