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 $65.66   5.461%   $69.2457   $69.25   $69.25   $69.20  
  Purchase #2 $210.76   9.295%   $230.3501   $230.35   $230.35   $230.40  
  Purchase #3 $81.80   10.466%   $90.3612   $90.36   $90.35   $90.40  
  Purchase #4 $171.99   11.351%   $191.5126   $191.51   $191.50   $191.50  
  Purchase #5 $236.86   6.549%   $252.372   $252.37   $252.35   $252.40  
  Purchase #6 $229.61   13.649%   $260.9495   $260.95   $260.95   $260.90  
  Purchase #7 $208.29   3.742%   $216.0842   $216.08   $216.10   $216.10  
  7 purchase totals = $1,204.97       $1,310.8753   $1,310.87   $1,310.85   $1,310.90