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 $216.75   9.194%   $236.678   $236.68   $236.70   $236.70  
  Purchase #2 $181.98   8.445%   $197.3482   $197.35   $197.35   $197.30  
  Purchase #3 $155.55   10.304%   $171.5779   $171.58   $171.60   $171.60  
  Purchase #4 $19.44   10.639%   $21.5082   $21.51   $21.50   $21.50  
  Purchase #5 $143.88   13.846%   $163.8016   $163.80   $163.80   $163.80  
  Purchase #6 $83.44   4.509%   $87.2023   $87.20   $87.20   $87.20  
  Purchase #7 $182.36   5.510%   $192.408   $192.41   $192.40   $192.40  
  7 purchase totals = $983.40       $1,070.5242   $1,070.53   $1,070.55   $1,070.50