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 $59.34   3.577%   $61.4626   $61.46   $61.45   $61.50  
  Purchase #2 $218.77   13.351%   $247.978   $247.98   $248.00   $248.00  
  Purchase #3 $132.34   12.332%   $148.6602   $148.66   $148.65   $148.70  
  Purchase #4 $96.80   10.540%   $107.0027   $107.00   $107.00   $107.00  
  Purchase #5 $144.57   8.800%   $157.2922   $157.29   $157.30   $157.30  
  Purchase #6 $213.34   10.292%   $235.297   $235.30   $235.30   $235.30  
  Purchase #7 $236.66   7.551%   $254.5302   $254.53   $254.55   $254.50  
  7 purchase totals = $1,101.82       $1,212.2229   $1,212.22   $1,212.25   $1,212.30