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 $43.88   6.363%   $46.6721   $46.67   $46.65   $46.70  
  Purchase #2 $129.60   9.345%   $141.7111   $141.71   $141.70   $141.70  
  Purchase #3 $65.26   9.869%   $71.7005   $71.70   $71.70   $71.70  
  Purchase #4 $29.37   7.153%   $31.4708   $31.47   $31.45   $31.50  
  Purchase #5 $198.53   3.579%   $205.6354   $205.64   $205.65   $205.60  
  Purchase #6 $11.88   13.493%   $13.483   $13.48   $13.50   $13.50  
  Purchase #7 $241.78   5.231%   $254.4275   $254.43   $254.45   $254.40  
  7 purchase totals = $720.30       $765.1004   $765.10   $765.10   $765.10