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 $168.35   11.205%   $187.2136   $187.21   $187.20   $187.20  
  Purchase #2 $188.67   13.798%   $214.7027   $214.70   $214.70   $214.70  
  Purchase #3 $43.79   6.418%   $46.6004   $46.60   $46.60   $46.60  
  Purchase #4 $51.55   5.361%   $54.3136   $54.31   $54.30   $54.30  
  Purchase #5 $244.81   6.391%   $260.4558   $260.46   $260.45   $260.50  
  Purchase #6 $242.27   6.362%   $257.6832   $257.68   $257.70   $257.70  
  Purchase #7 $153.83   12.823%   $173.5556   $173.56   $173.55   $173.60  
  7 purchase totals = $1,093.27       $1,194.5249   $1,194.52   $1,194.50   $1,194.60