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 $58.96   5.200%   $62.0259   $62.03   $62.05   $62.00  
  Purchase #2 $117.92   6.225%   $125.2605   $125.26   $125.25   $125.30  
  Purchase #3 $57.65   5.109%   $60.5953   $60.60   $60.60   $60.60  
  Purchase #4 $21.64   6.363%   $23.017   $23.02   $23.00   $23.00  
  Purchase #5 $231.26   9.243%   $252.6354   $252.64   $252.65   $252.60  
  Purchase #6 $108.46   8.224%   $117.3798   $117.38   $117.40   $117.40  
  Purchase #7 $111.80   3.467%   $115.6761   $115.68   $115.70   $115.70  
  7 purchase totals = $707.69       $756.5900   $756.61   $756.65   $756.60