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 $169.76   3.654%   $175.963   $175.96   $175.95   $176.00  
  Purchase #2 $54.26   4.567%   $56.7381   $56.74   $56.75   $56.70  
  Purchase #3 $47.53   11.320%   $52.9104   $52.91   $52.90   $52.90  
  Purchase #4 $182.37   7.285%   $195.6557   $195.66   $195.65   $195.70  
  Purchase #5 $36.86   8.549%   $40.0112   $40.01   $40.00   $40.00  
  Purchase #6 $56.49   11.145%   $62.7858   $62.79   $62.80   $62.80  
  Purchase #7 $162.55   5.191%   $170.988   $170.99   $171.00   $171.00  
  7 purchase totals = $709.82       $755.0522   $755.06   $755.05   $755.10