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 $214.67   5.864%   $227.2582   $227.26   $227.25   $227.30  
  Purchase #2 $117.73   13.427%   $133.5376   $133.54   $133.55   $133.50  
  Purchase #3 $181.43   4.653%   $189.8719   $189.87   $189.85   $189.90  
  Purchase #4 $204.53   11.591%   $228.2371   $228.24   $228.25   $228.20  
  Purchase #5 $158.72   12.718%   $178.906   $178.91   $178.90   $178.90  
  Purchase #6 $104.61   9.634%   $114.6881   $114.69   $114.70   $114.70  
  Purchase #7 $96.96   13.597%   $110.1437   $110.14   $110.15   $110.10  
  7 purchase totals = $1,078.65       $1,182.6426   $1,182.65   $1,182.65   $1,182.60