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 $68.32   11.705%   $76.3169   $76.32   $76.30   $76.30  
  Purchase #2 $43.38   12.192%   $48.6689   $48.67   $48.65   $48.70  
  Purchase #3 $183.73   4.526%   $192.0456   $192.05   $192.05   $192.00  
  Purchase #4 $33.39   6.561%   $35.5807   $35.58   $35.60   $35.60  
  Purchase #5 $142.43   9.713%   $156.2642   $156.26   $156.25   $156.30  
  Purchase #6 $124.29   12.323%   $139.6063   $139.61   $139.60   $139.60  
  Purchase #7 $212.59   7.511%   $228.5576   $228.56   $228.55   $228.60  
  7 purchase totals = $808.13       $877.0402   $877.05   $877.00   $877.10