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 $192.99   7.284%   $207.0474   $207.05   $207.05   $207.00  
  Purchase #2 $232.67   13.267%   $263.5383   $263.54   $263.55   $263.50  
  Purchase #3 $26.29   13.157%   $29.749   $29.75   $29.75   $29.70  
  Purchase #4 $161.60   9.593%   $177.1023   $177.10   $177.10   $177.10  
  Purchase #5 $135.61   10.129%   $149.3459   $149.35   $149.35   $149.30  
  Purchase #6 $91.44   3.522%   $94.6605   $94.66   $94.65   $94.70  
  Purchase #7 $209.77   13.871%   $238.8672   $238.87   $238.85   $238.90  
  7 purchase totals = $1,050.37       $1,160.3106   $1,160.32   $1,160.30   $1,160.20