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 $232.96   12.765%   $262.6973   $262.70   $262.70   $262.70  
  Purchase #2 $106.92   3.673%   $110.8472   $110.85   $110.85   $110.80  
  Purchase #3 $175.64   7.265%   $188.4002   $188.40   $188.40   $188.40  
  Purchase #4 $202.64   11.853%   $226.6589   $226.66   $226.65   $226.70  
  Purchase #5 $134.92   5.683%   $142.5875   $142.59   $142.60   $142.60  
  Purchase #6 $199.30   6.750%   $212.7528   $212.75   $212.75   $212.80  
  Purchase #7 $235.54   12.163%   $264.1887   $264.19   $264.20   $264.20  
  7 purchase totals = $1,287.92       $1,408.1326   $1,408.14   $1,408.15   $1,408.20