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 $218.72   7.668%   $235.4914   $235.49   $235.50   $235.50  
  Purchase #2 $55.84   11.288%   $62.1432   $62.14   $62.15   $62.10  
  Purchase #3 $66.38   11.747%   $74.1777   $74.18   $74.20   $74.20  
  Purchase #4 $88.89   7.305%   $95.3834   $95.38   $95.40   $95.40  
  Purchase #5 $161.42   8.520%   $175.173   $175.17   $175.15   $175.20  
  Purchase #6 $204.54   7.743%   $220.3775   $220.38   $220.40   $220.40  
  Purchase #7 $205.52   3.761%   $213.2496   $213.25   $213.25   $213.20  
  7 purchase totals = $1,001.31       $1,075.9958   $1,075.99   $1,076.05   $1,076.00