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 $233.36   5.356%   $245.8588   $245.86   $245.85   $245.90  
  Purchase #2 $86.57   5.348%   $91.1998   $91.20   $91.20   $91.20  
  Purchase #3 $71.36   3.654%   $73.9675   $73.97   $73.95   $74.00  
  Purchase #4 $190.91   6.134%   $202.6204   $202.62   $202.60   $202.60  
  Purchase #5 $32.55   5.618%   $34.3787   $34.38   $34.40   $34.40  
  Purchase #6 $58.85   7.229%   $63.1043   $63.10   $63.10   $63.10  
  Purchase #7 $131.71   3.648%   $136.5148   $136.51   $136.50   $136.50  
  7 purchase totals = $805.31       $847.6443   $847.64   $847.60   $847.70