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 $177.88   3.235%   $183.6344   $183.63   $183.65   $183.60  
  Purchase #2 $217.90   3.574%   $225.6877   $225.69   $225.70   $225.70  
  Purchase #3 $186.49   13.283%   $211.2615   $211.26   $211.25   $211.30  
  Purchase #4 $205.99   5.176%   $216.652   $216.65   $216.65   $216.70  
  Purchase #5 $158.93   9.471%   $173.9823   $173.98   $174.00   $174.00  
  Purchase #6 $181.43   10.762%   $200.9555   $200.96   $200.95   $201.00  
  Purchase #7 $206.40   12.625%   $232.458   $232.46   $232.45   $232.50  
  7 purchase totals = $1,335.02       $1,444.6314   $1,444.63   $1,444.65   $1,444.80