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 $83.91   12.125%   $94.0841   $94.08   $94.10   $94.10  
  Purchase #2 $143.48   3.478%   $148.4702   $148.47   $148.45   $148.50  
  Purchase #3 $22.97   5.731%   $24.2864   $24.29   $24.30   $24.30  
  Purchase #4 $220.97   7.382%   $237.282   $237.28   $237.30   $237.30  
  Purchase #5 $228.78   10.549%   $252.914   $252.91   $252.90   $252.90  
  Purchase #6 $186.70   11.582%   $208.3236   $208.32   $208.30   $208.30  
  Purchase #7 $65.63   6.809%   $70.0987   $70.10   $70.10   $70.10  
  7 purchase totals = $952.44       $1,035.4590   $1,035.45   $1,035.45   $1,035.50