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 $119.56   4.847%   $125.3551   $125.36   $125.35   $125.40  
  Purchase #2 $184.29   9.261%   $201.3571   $201.36   $201.35   $201.40  
  Purchase #3 $249.36   6.139%   $264.6682   $264.67   $264.65   $264.70  
  Purchase #4 $236.65   6.414%   $251.8287   $251.83   $251.85   $251.80  
  Purchase #5 $102.91   11.348%   $114.5882   $114.59   $114.60   $114.60  
  Purchase #6 $22.69   13.727%   $25.8047   $25.80   $25.80   $25.80  
  Purchase #7 $168.86   9.132%   $184.2803   $184.28   $184.30   $184.30  
  7 purchase totals = $1,084.32       $1,167.8823   $1,167.89   $1,167.90   $1,168.00