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 $58.27   6.835%   $62.2528   $62.25   $62.25   $62.30  
  Purchase #2 $8.92   7.747%   $9.611   $9.61   $9.60   $9.60  
  Purchase #3 $44.58   6.115%   $47.3061   $47.31   $47.30   $47.30  
  Purchase #4 $124.64   5.208%   $131.1313   $131.13   $131.15   $131.10  
  Purchase #5 $189.72   12.563%   $213.5545   $213.55   $213.55   $213.60  
  Purchase #6 $234.38   5.458%   $247.1725   $247.17   $247.15   $247.20  
  Purchase #7 $42.57   5.770%   $45.0263   $45.03   $45.05   $45.00  
  7 purchase totals = $703.08       $756.0545   $756.05   $756.05   $756.10