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 $63.66   12.392%   $71.5487   $71.55   $71.55   $71.50  
  Purchase #2 $168.78   8.740%   $183.5314   $183.53   $183.55   $183.50  
  Purchase #3 $163.80   3.541%   $169.6002   $169.60   $169.60   $169.60  
  Purchase #4 $244.28   11.416%   $272.167   $272.17   $272.15   $272.20  
  Purchase #5 $76.60   4.787%   $80.2668   $80.27   $80.25   $80.30  
  Purchase #6 $91.43   6.226%   $97.1224   $97.12   $97.10   $97.10  
  Purchase #7 $155.46   3.518%   $160.9291   $160.93   $160.95   $160.90  
  7 purchase totals = $964.01       $1,035.1656   $1,035.17   $1,035.15   $1,035.10