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 $70.46   4.504%   $73.6335   $73.63   $73.65   $73.60  
  Purchase #2 $140.56   9.248%   $153.559   $153.56   $153.55   $153.60  
  Purchase #3 $76.95   9.670%   $84.3911   $84.39   $84.40   $84.40  
  Purchase #4 $228.61   13.597%   $259.6941   $259.69   $259.70   $259.70  
  Purchase #5 $151.96   10.638%   $168.1255   $168.13   $168.15   $168.10  
  Purchase #6 $228.59   10.714%   $253.0811   $253.08   $253.10   $253.10  
  Purchase #7 $166.34   3.451%   $172.0804   $172.08   $172.10   $172.10  
  7 purchase totals = $1,063.47       $1,164.5647   $1,164.56   $1,164.65   $1,164.60