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 $162.49   4.660%   $170.062   $170.06   $170.05   $170.10  
  Purchase #2 $87.40   12.110%   $97.9841   $97.98   $98.00   $98.00  
  Purchase #3 $69.79   8.864%   $75.9762   $75.98   $76.00   $76.00  
  Purchase #4 $244.87   9.517%   $268.1743   $268.17   $268.15   $268.20  
  Purchase #5 $53.95   3.336%   $55.7498   $55.75   $55.75   $55.70  
  Purchase #6 $161.54   8.440%   $175.174   $175.17   $175.15   $175.20  
  Purchase #7 $175.31   10.734%   $194.1278   $194.13   $194.15   $194.10  
  7 purchase totals = $955.35       $1,037.2482   $1,037.24   $1,037.25   $1,037.30