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 $195.29   5.552%   $206.1325   $206.13   $206.15   $206.10  
  Purchase #2 $208.70   11.330%   $232.3457   $232.35   $232.35   $232.30  
  Purchase #3 $70.64   6.266%   $75.0663   $75.07   $75.05   $75.10  
  Purchase #4 $38.57   13.503%   $43.7781   $43.78   $43.80   $43.80  
  Purchase #5 $171.26   8.365%   $185.5859   $185.59   $185.60   $185.60  
  Purchase #6 $59.65   4.405%   $62.2776   $62.28   $62.30   $62.30  
  Purchase #7 $82.88   9.549%   $90.7942   $90.79   $90.80   $90.80  
  7 purchase totals = $826.99       $895.9803   $895.99   $896.05   $896.00