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 $118.33   5.606%   $124.9636   $124.96   $124.95   $125.00  
  Purchase #2 $137.57   5.725%   $145.4459   $145.45   $145.45   $145.40  
  Purchase #3 $177.83   8.815%   $193.5057   $193.51   $193.50   $193.50  
  Purchase #4 $49.74   6.263%   $52.8552   $52.86   $52.85   $52.90  
  Purchase #5 $133.78   13.673%   $152.0717   $152.07   $152.05   $152.10  
  Purchase #6 $148.37   9.623%   $162.6476   $162.65   $162.65   $162.60  
  Purchase #7 $190.88   4.233%   $198.96   $198.96   $198.95   $199.00  
  7 purchase totals = $956.50       $1,030.4497   $1,030.46   $1,030.40   $1,030.50