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 $216.78   11.470%   $241.6447   $241.64   $241.65   $241.60  
  Purchase #2 $200.67   8.251%   $217.2273   $217.23   $217.25   $217.20  
  Purchase #3 $214.44   13.364%   $243.0978   $243.10   $243.10   $243.10  
  Purchase #4 $203.68   9.171%   $222.3595   $222.36   $222.35   $222.40  
  Purchase #5 $178.45   7.414%   $191.6803   $191.68   $191.70   $191.70  
  Purchase #6 $228.25   6.670%   $243.4743   $243.47   $243.45   $243.50  
  Purchase #7 $70.95   7.581%   $76.3287   $76.33   $76.35   $76.30  
  7 purchase totals = $1,313.22       $1,435.8126   $1,435.81   $1,435.85   $1,435.80