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 $227.66   8.514%   $247.043   $247.04   $247.05   $247.00  
  Purchase #2 $145.44   5.674%   $153.6923   $153.69   $153.70   $153.70  
  Purchase #3 $194.54   4.188%   $202.6873   $202.69   $202.70   $202.70  
  Purchase #4 $82.77   12.469%   $93.0906   $93.09   $93.10   $93.10  
  Purchase #5 $109.54   9.830%   $120.3078   $120.31   $120.30   $120.30  
  Purchase #6 $246.27   3.827%   $255.6948   $255.69   $255.70   $255.70  
  Purchase #7 $155.34   4.691%   $162.627   $162.63   $162.65   $162.60  
  7 purchase totals = $1,161.56       $1,235.1428   $1,235.14   $1,235.20   $1,235.10