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 $58.48   9.822%   $64.2239   $64.22   $64.20   $64.20  
  Purchase #2 $147.47   6.835%   $157.5496   $157.55   $157.55   $157.50  
  Purchase #3 $85.33   8.139%   $92.275   $92.28   $92.30   $92.30  
  Purchase #4 $218.86   10.174%   $241.1268   $241.13   $241.15   $241.10  
  Purchase #5 $164.34   6.190%   $174.5126   $174.51   $174.50   $174.50  
  Purchase #6 $130.74   7.551%   $140.6122   $140.61   $140.60   $140.60  
  Purchase #7 $216.88   3.638%   $224.7701   $224.77   $224.75   $224.80  
  7 purchase totals = $1,022.10       $1,095.0702   $1,095.07   $1,095.05   $1,095.00