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 $211.85   7.409%   $227.546   $227.55   $227.55   $227.50  
  Purchase #2 $178.36   5.398%   $187.9879   $187.99   $188.00   $188.00  
  Purchase #3 $34.99   9.592%   $38.3462   $38.35   $38.35   $38.30  
  Purchase #4 $156.89   4.579%   $164.074   $164.07   $164.05   $164.10  
  Purchase #5 $160.44   10.166%   $176.7503   $176.75   $176.75   $176.80  
  Purchase #6 $101.93   11.306%   $113.4542   $113.45   $113.45   $113.50  
  Purchase #7 $195.58   5.508%   $206.3525   $206.35   $206.35   $206.40  
  7 purchase totals = $1,040.04       $1,114.5111   $1,114.51   $1,114.50   $1,114.60