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 $211.83   9.613%   $232.1932   $232.19   $232.20   $232.20  
  Purchase #2 $82.98   4.118%   $86.3971   $86.40   $86.40   $86.40  
  Purchase #3 $178.48   11.861%   $199.6495   $199.65   $199.65   $199.60  
  Purchase #4 $113.66   4.481%   $118.7531   $118.75   $118.75   $118.80  
  Purchase #5 $55.53   5.244%   $58.442   $58.44   $58.45   $58.40  
  Purchase #6 $170.30   6.255%   $180.9523   $180.95   $180.95   $181.00  
  Purchase #7 $143.31   5.868%   $151.7194   $151.72   $151.70   $151.70  
  7 purchase totals = $956.09       $1,028.1066   $1,028.10   $1,028.10   $1,028.10