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 $34.94   7.530%   $37.571   $37.57   $37.55   $37.60  
  Purchase #2 $120.59   4.462%   $125.9707   $125.97   $125.95   $126.00  
  Purchase #3 $187.51   7.348%   $201.2882   $201.29   $201.30   $201.30  
  Purchase #4 $136.61   13.837%   $155.5127   $155.51   $155.50   $155.50  
  Purchase #5 $123.83   4.383%   $129.2575   $129.26   $129.25   $129.30  
  Purchase #6 $242.43   5.328%   $255.3467   $255.35   $255.35   $255.30  
  Purchase #7 $225.95   10.525%   $249.7312   $249.73   $249.75   $249.70  
  7 purchase totals = $1,071.86       $1,154.6780   $1,154.68   $1,154.65   $1,154.70