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 $156.53   11.385%   $174.3509   $174.35   $174.35   $174.40  
  Purchase #2 $166.27   10.728%   $184.1074   $184.11   $184.10   $184.10  
  Purchase #3 $17.25   10.512%   $19.0633   $19.06   $19.05   $19.10  
  Purchase #4 $94.37   3.550%   $97.7201   $97.72   $97.70   $97.70  
  Purchase #5 $248.40   3.795%   $257.8268   $257.83   $257.85   $257.80  
  Purchase #6 $50.92   5.519%   $53.7303   $53.73   $53.75   $53.70  
  Purchase #7 $158.39   5.205%   $166.6342   $166.63   $166.65   $166.60  
  7 purchase totals = $892.13       $953.4330   $953.43   $953.45   $953.40