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 $88.63   7.780%   $95.5254   $95.53   $95.55   $95.50  
  Purchase #2 $32.57   5.185%   $34.2588   $34.26   $34.25   $34.30  
  Purchase #3 $10.88   11.266%   $12.1057   $12.11   $12.10   $12.10  
  Purchase #4 $32.59   3.244%   $33.6472   $33.65   $33.65   $33.60  
  Purchase #5 $214.34   4.511%   $224.0089   $224.01   $224.00   $224.00  
  Purchase #6 $195.44   12.871%   $220.5951   $220.60   $220.60   $220.60  
  Purchase #7 $102.48   9.483%   $112.1982   $112.20   $112.20   $112.20  
  7 purchase totals = $676.93       $732.3393   $732.36   $732.35   $732.30