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 $194.38   8.683%   $211.258   $211.26   $211.25   $211.30  
  Purchase #2 $141.75   8.234%   $153.4217   $153.42   $153.40   $153.40  
  Purchase #3 $94.91   10.180%   $104.5718   $104.57   $104.55   $104.60  
  Purchase #4 $244.57   13.132%   $276.6869   $276.69   $276.70   $276.70  
  Purchase #5 $241.76   4.458%   $252.5377   $252.54   $252.55   $252.50  
  Purchase #6 $139.48   11.615%   $155.6806   $155.68   $155.70   $155.70  
  Purchase #7 $184.43   13.128%   $208.642   $208.64   $208.65   $208.60  
  7 purchase totals = $1,241.28       $1,362.7987   $1,362.80   $1,362.80   $1,362.80