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 $59.34   4.565%   $62.0489   $62.05   $62.05   $62.00  
  Purchase #2 $227.45   13.569%   $258.3127   $258.31   $258.30   $258.30  
  Purchase #3 $240.88   13.209%   $272.6978   $272.70   $272.70   $272.70  
  Purchase #4 $44.62   10.312%   $49.2212   $49.22   $49.20   $49.20  
  Purchase #5 $20.61   9.620%   $22.5927   $22.59   $22.60   $22.60  
  Purchase #6 $7.97   6.516%   $8.4893   $8.49   $8.50   $8.50  
  Purchase #7 $175.67   11.637%   $196.1127   $196.11   $196.10   $196.10  
  7 purchase totals = $776.54       $869.4753   $869.47   $869.45   $869.40