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 $119.64   4.737%   $125.3073   $125.31   $125.30   $125.30  
  Purchase #2 $80.33   5.749%   $84.9482   $84.95   $84.95   $84.90  
  Purchase #3 $192.44   3.352%   $198.8906   $198.89   $198.90   $198.90  
  Purchase #4 $166.32   5.198%   $174.9653   $174.97   $174.95   $175.00  
  Purchase #5 $202.59   10.215%   $223.2846   $223.28   $223.30   $223.30  
  Purchase #6 $203.47   3.389%   $210.3656   $210.37   $210.35   $210.40  
  Purchase #7 $6.58   6.687%   $7.02   $7.02   $7.00   $7.00  
  7 purchase totals = $971.37       $1,024.7816   $1,024.79   $1,024.75   $1,024.80