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 $53.87   13.715%   $61.2583   $61.26   $61.25   $61.30  
  Purchase #2 $100.29   11.128%   $111.4503   $111.45   $111.45   $111.50  
  Purchase #3 $244.81   6.433%   $260.5586   $260.56   $260.55   $260.60  
  Purchase #4 $215.44   6.841%   $230.1783   $230.18   $230.20   $230.20  
  Purchase #5 $115.49   4.209%   $120.351   $120.35   $120.35   $120.40  
  Purchase #6 $57.48   12.660%   $64.757   $64.76   $64.75   $64.80  
  Purchase #7 $192.40   6.351%   $204.6193   $204.62   $204.60   $204.60  
  7 purchase totals = $979.78       $1,053.1728   $1,053.18   $1,053.15   $1,053.40