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 $55.59   5.670%   $58.742   $58.74   $58.75   $58.70  
  Purchase #2 $45.54   3.861%   $47.2983   $47.30   $47.30   $47.30  
  Purchase #3 $160.73   6.759%   $171.5937   $171.59   $171.60   $171.60  
  Purchase #4 $226.77   13.800%   $258.0643   $258.06   $258.05   $258.10  
  Purchase #5 $204.47   4.218%   $213.0945   $213.09   $213.10   $213.10  
  Purchase #6 $56.51   6.156%   $59.9888   $59.99   $60.00   $60.00  
  Purchase #7 $132.25   3.249%   $136.5468   $136.55   $136.55   $136.50  
  7 purchase totals = $881.86       $945.3284   $945.32   $945.35   $945.30