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 $88.75   6.443%   $94.4682   $94.47   $94.45   $94.50  
  Purchase #2 $153.97   13.392%   $174.5897   $174.59   $174.60   $174.60  
  Purchase #3 $186.61   11.622%   $208.2978   $208.30   $208.30   $208.30  
  Purchase #4 $58.51   7.791%   $63.0685   $63.07   $63.05   $63.10  
  Purchase #5 $190.33   10.835%   $210.9523   $210.95   $210.95   $211.00  
  Purchase #6 $217.54   13.213%   $246.2836   $246.28   $246.30   $246.30  
  Purchase #7 $195.66   6.183%   $207.7577   $207.76   $207.75   $207.80  
  7 purchase totals = $1,091.37       $1,205.4178   $1,205.42   $1,205.40   $1,205.60