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 $44.35   6.523%   $47.243   $47.24   $47.25   $47.20  
  Purchase #2 $248.75   4.652%   $260.3219   $260.32   $260.30   $260.30  
  Purchase #3 $22.41   12.411%   $25.1913   $25.19   $25.20   $25.20  
  Purchase #4 $206.32   12.702%   $232.5268   $232.53   $232.55   $232.50  
  Purchase #5 $245.63   7.577%   $264.2414   $264.24   $264.25   $264.20  
  Purchase #6 $122.60   9.391%   $134.1134   $134.11   $134.10   $134.10  
  Purchase #7 $102.54   8.238%   $110.9872   $110.99   $111.00   $111.00  
  7 purchase totals = $992.60       $1,074.6250   $1,074.62   $1,074.65   $1,074.50