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 $87.46   5.611%   $92.3674   $92.37   $92.35   $92.40  
  Purchase #2 $106.86   11.349%   $118.9875   $118.99   $119.00   $119.00  
  Purchase #3 $218.33   5.779%   $230.9473   $230.95   $230.95   $230.90  
  Purchase #4 $217.95   8.257%   $235.9461   $235.95   $235.95   $235.90  
  Purchase #5 $182.47   13.453%   $207.0177   $207.02   $207.00   $207.00  
  Purchase #6 $101.60   8.373%   $110.107   $110.11   $110.10   $110.10  
  Purchase #7 $215.81   5.636%   $227.9731   $227.97   $227.95   $228.00  
  7 purchase totals = $1,130.48       $1,223.3461   $1,223.36   $1,223.30   $1,223.30