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 $29.80   9.427%   $32.6092   $32.61   $32.60   $32.60  
  Purchase #2 $51.55   10.218%   $56.8174   $56.82   $56.80   $56.80  
  Purchase #3 $53.48   9.110%   $58.352   $58.35   $58.35   $58.40  
  Purchase #4 $70.72   7.316%   $75.8939   $75.89   $75.90   $75.90  
  Purchase #5 $126.63   11.427%   $141.1   $141.10   $141.10   $141.10  
  Purchase #6 $57.49   7.205%   $61.6322   $61.63   $61.65   $61.60  
  Purchase #7 $38.80   7.179%   $41.5855   $41.59   $41.60   $41.60  
  7 purchase totals = $428.47       $467.9902   $467.99   $468.00   $468.00