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 $41.25   12.233%   $46.2961   $46.30   $46.30   $46.30  
  Purchase #2 $94.98   6.577%   $101.2268   $101.23   $101.25   $101.20  
  Purchase #3 $161.57   6.400%   $171.9105   $171.91   $171.90   $171.90  
  Purchase #4 $232.96   7.337%   $250.0523   $250.05   $250.05   $250.10  
  Purchase #5 $8.42   6.562%   $8.9725   $8.97   $8.95   $9.00  
  Purchase #6 $197.84   10.865%   $219.3353   $219.34   $219.35   $219.30  
  Purchase #7 $147.30   5.326%   $155.1452   $155.15   $155.15   $155.10  
  7 purchase totals = $884.32       $952.9387   $952.95   $952.95   $952.90