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 $61.96   11.825%   $69.2868   $69.29   $69.30   $69.30  
  Purchase #2 $234.52   7.867%   $252.9697   $252.97   $252.95   $253.00  
  Purchase #3 $139.65   12.210%   $156.7013   $156.70   $156.70   $156.70  
  Purchase #4 $30.65   5.227%   $32.2521   $32.25   $32.25   $32.30  
  Purchase #5 $197.67   13.754%   $224.8575   $224.86   $224.85   $224.90  
  Purchase #6 $228.51   8.285%   $247.4421   $247.44   $247.45   $247.40  
  Purchase #7 $153.83   4.422%   $160.6324   $160.63   $160.65   $160.60  
  7 purchase totals = $1,046.79       $1,144.1419   $1,144.14   $1,144.15   $1,144.20