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 $197.25   8.265%   $213.5527   $213.55   $213.55   $213.60  
  Purchase #2 $216.71   5.137%   $227.8424   $227.84   $227.85   $227.80  
  Purchase #3 $69.26   11.414%   $77.1653   $77.17   $77.15   $77.20  
  Purchase #4 $152.44   6.553%   $162.4294   $162.43   $162.45   $162.40  
  Purchase #5 $96.61   10.355%   $106.614   $106.61   $106.60   $106.60  
  Purchase #6 $220.56   3.215%   $227.651   $227.65   $227.65   $227.70  
  Purchase #7 $55.54   8.623%   $60.3292   $60.33   $60.35   $60.30  
  7 purchase totals = $1,008.37       $1,075.5840   $1,075.58   $1,075.60   $1,075.60