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 $214.57   9.798%   $235.5936   $235.59   $235.60   $235.60  
  Purchase #2 $118.67   4.215%   $123.6719   $123.67   $123.65   $123.70  
  Purchase #3 $218.67   4.251%   $227.9657   $227.97   $227.95   $228.00  
  Purchase #4 $171.95   13.682%   $195.4762   $195.48   $195.50   $195.50  
  Purchase #5 $145.61   7.300%   $156.2395   $156.24   $156.25   $156.20  
  Purchase #6 $208.59   4.578%   $218.1393   $218.14   $218.15   $218.10  
  Purchase #7 $199.83   9.790%   $219.3934   $219.39   $219.40   $219.40  
  7 purchase totals = $1,277.89       $1,376.4796   $1,376.48   $1,376.50   $1,376.50