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 $114.36   10.188%   $126.011   $126.01   $126.00   $126.00  
  Purchase #2 $153.58   11.229%   $170.8255   $170.83   $170.85   $170.80  
  Purchase #3 $169.93   3.511%   $175.8962   $175.90   $175.90   $175.90  
  Purchase #4 $35.81   12.403%   $40.2515   $40.25   $40.25   $40.30  
  Purchase #5 $119.62   10.819%   $132.5617   $132.56   $132.55   $132.60  
  Purchase #6 $6.40   7.115%   $6.8554   $6.86   $6.85   $6.90  
  Purchase #7 $109.35   4.669%   $114.4556   $114.46   $114.45   $114.50  
  7 purchase totals = $709.05       $766.8569   $766.87   $766.85   $767.00