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 $91.95   4.627%   $96.2045   $96.20   $96.20   $96.20  
  Purchase #2 $22.69   5.776%   $24.0006   $24.00   $24.00   $24.00  
  Purchase #3 $241.46   3.626%   $250.2153   $250.22   $250.20   $250.20  
  Purchase #4 $54.77   8.233%   $59.2792   $59.28   $59.30   $59.30  
  Purchase #5 $55.51   10.586%   $61.3863   $61.39   $61.40   $61.40  
  Purchase #6 $240.27   9.741%   $263.6747   $263.67   $263.65   $263.70  
  Purchase #7 $160.88   12.689%   $181.2941   $181.29   $181.30   $181.30  
  7 purchase totals = $867.53       $936.0547   $936.05   $936.05   $936.10