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 $231.65   5.337%   $244.0132   $244.01   $244.00   $244.00  
  Purchase #2 $209.81   9.279%   $229.2783   $229.28   $229.30   $229.30  
  Purchase #3 $64.91   11.738%   $72.5291   $72.53   $72.55   $72.50  
  Purchase #4 $194.59   6.509%   $207.2559   $207.26   $207.25   $207.30  
  Purchase #5 $93.76   7.131%   $100.446   $100.45   $100.45   $100.40  
  Purchase #6 $20.86   6.270%   $22.1679   $22.17   $22.15   $22.20  
  Purchase #7 $241.49   6.143%   $256.3247   $256.32   $256.30   $256.30  
  7 purchase totals = $1,057.07       $1,132.0151   $1,132.02   $1,132.00   $1,132.00