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 $165.97   10.245%   $182.9736   $182.97   $182.95   $183.00  
  Purchase #2 $33.39   12.630%   $37.6072   $37.61   $37.60   $37.60  
  Purchase #3 $107.51   11.590%   $119.9704   $119.97   $119.95   $120.00  
  Purchase #4 $227.96   10.534%   $251.9733   $251.97   $251.95   $252.00  
  Purchase #5 $200.80   11.819%   $224.5326   $224.53   $224.55   $224.50  
  Purchase #6 $134.88   4.556%   $141.0251   $141.03   $141.05   $141.00  
  Purchase #7 $193.88   6.475%   $206.4337   $206.43   $206.45   $206.40  
  7 purchase totals = $1,064.39       $1,164.5159   $1,164.51   $1,164.50   $1,164.50