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 $248.34   5.533%   $262.0807   $262.08   $262.10   $262.10  
  Purchase #2 $247.57   6.470%   $263.5878   $263.59   $263.60   $263.60  
  Purchase #3 $81.71   6.664%   $87.1552   $87.16   $87.15   $87.20  
  Purchase #4 $60.73   6.561%   $64.7145   $64.71   $64.70   $64.70  
  Purchase #5 $213.49   9.608%   $234.0021   $234.00   $234.00   $234.00  
  Purchase #6 $71.75   13.262%   $81.2655   $81.27   $81.25   $81.30  
  Purchase #7 $90.91   4.532%   $95.03   $95.03   $95.05   $95.00  
  7 purchase totals = $1,014.50       $1,087.8358   $1,087.84   $1,087.85   $1,087.90