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 $88.52   9.181%   $96.647   $96.65   $96.65   $96.60  
  Purchase #2 $65.33   12.158%   $73.2728   $73.27   $73.25   $73.30  
  Purchase #3 $22.46   5.381%   $23.6686   $23.67   $23.65   $23.70  
  Purchase #4 $159.43   13.449%   $180.8717   $180.87   $180.85   $180.90  
  Purchase #5 $180.33   7.182%   $193.2813   $193.28   $193.30   $193.30  
  Purchase #6 $210.32   9.580%   $230.4687   $230.47   $230.45   $230.50  
  Purchase #7 $229.48   13.745%   $261.022   $261.02   $261.00   $261.00  
  7 purchase totals = $955.87       $1,059.2321   $1,059.23   $1,059.15   $1,059.30