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 $126.34   8.700%   $137.3316   $137.33   $137.35   $137.30  
  Purchase #2 $212.28   9.288%   $231.9966   $232.00   $232.00   $232.00  
  Purchase #3 $68.57   8.479%   $74.3841   $74.38   $74.40   $74.40  
  Purchase #4 $94.38   3.311%   $97.5049   $97.50   $97.50   $97.50  
  Purchase #5 $221.72   9.353%   $242.4575   $242.46   $242.45   $242.50  
  Purchase #6 $44.33   6.170%   $47.0652   $47.07   $47.05   $47.10  
  Purchase #7 $228.57   5.826%   $241.8865   $241.89   $241.90   $241.90  
  7 purchase totals = $996.19       $1,072.6264   $1,072.63   $1,072.65   $1,072.70