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 $32.81   13.233%   $37.1517   $37.15   $37.15   $37.20  
  Purchase #2 $247.95   6.411%   $263.8461   $263.85   $263.85   $263.80  
  Purchase #3 $157.84   4.456%   $164.8734   $164.87   $164.85   $164.90  
  Purchase #4 $131.69   10.487%   $145.5003   $145.50   $145.50   $145.50  
  Purchase #5 $175.42   5.210%   $184.5594   $184.56   $184.55   $184.60  
  Purchase #6 $216.64   3.831%   $224.9395   $224.94   $224.95   $224.90  
  Purchase #7 $101.72   3.399%   $105.1775   $105.18   $105.20   $105.20  
  7 purchase totals = $1,064.07       $1,126.0479   $1,126.05   $1,126.05   $1,126.10