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 $113.72   4.810%   $119.1899   $119.19   $119.20   $119.20  
  Purchase #2 $98.75   12.195%   $110.7926   $110.79   $110.80   $110.80  
  Purchase #3 $230.84   7.225%   $247.5182   $247.52   $247.50   $247.50  
  Purchase #4 $158.53   10.815%   $175.675   $175.68   $175.70   $175.70  
  Purchase #5 $72.34   3.186%   $74.6448   $74.64   $74.65   $74.60  
  Purchase #6 $237.68   6.728%   $253.6711   $253.67   $253.65   $253.70  
  Purchase #7 $167.62   10.425%   $185.0944   $185.09   $185.10   $185.10  
  7 purchase totals = $1,079.48       $1,166.5860   $1,166.58   $1,166.60   $1,166.60