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 $35.98   5.865%   $38.0902   $38.09   $38.10   $38.10  
  Purchase #2 $53.64   10.194%   $59.1081   $59.11   $59.10   $59.10  
  Purchase #3 $27.71   4.594%   $28.983   $28.98   $29.00   $29.00  
  Purchase #4 $224.34   6.581%   $239.1038   $239.10   $239.10   $239.10  
  Purchase #5 $184.30   7.384%   $197.9087   $197.91   $197.90   $197.90  
  Purchase #6 $149.25   6.376%   $158.7662   $158.77   $158.75   $158.80  
  Purchase #7 $22.94   4.837%   $24.0496   $24.05   $24.05   $24.00  
  7 purchase totals = $698.16       $746.0096   $746.01   $746.00   $746.00