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 $240.65   9.263%   $262.9414   $262.94   $262.95   $262.90  
  Purchase #2 $97.79   8.575%   $106.1755   $106.18   $106.20   $106.20  
  Purchase #3 $166.81   9.429%   $182.5385   $182.54   $182.55   $182.50  
  Purchase #4 $161.68   8.591%   $175.5699   $175.57   $175.55   $175.60  
  Purchase #5 $8.69   10.621%   $9.613   $9.61   $9.60   $9.60  
  Purchase #6 $158.64   9.454%   $173.6378   $173.64   $173.65   $173.60  
  Purchase #7 $39.76   6.492%   $42.3412   $42.34   $42.35   $42.30  
  7 purchase totals = $874.02       $952.8173   $952.82   $952.85   $952.70