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 $222.99   9.425%   $244.0068   $244.01   $244.00   $244.00  
  Purchase #2 $88.75   4.562%   $92.7988   $92.80   $92.80   $92.80  
  Purchase #3 $19.53   6.335%   $20.7672   $20.77   $20.75   $20.80  
  Purchase #4 $15.74   6.690%   $16.793   $16.79   $16.80   $16.80  
  Purchase #5 $34.34   6.632%   $36.6174   $36.62   $36.60   $36.60  
  Purchase #6 $9.72   3.460%   $10.0563   $10.06   $10.05   $10.10  
  Purchase #7 $42.65   7.720%   $45.9426   $45.94   $45.95   $45.90  
  7 purchase totals = $433.72       $466.9821   $466.99   $466.95   $467.00