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 $187.86   10.516%   $207.6154   $207.62   $207.60   $207.60  
  Purchase #2 $155.36   12.183%   $174.2875   $174.29   $174.30   $174.30  
  Purchase #3 $142.56   8.726%   $154.9998   $155.00   $155.00   $155.00  
  Purchase #4 $71.25   6.128%   $75.6162   $75.62   $75.60   $75.60  
  Purchase #5 $127.50   10.510%   $140.9003   $140.90   $140.90   $140.90  
  Purchase #6 $231.26   8.191%   $250.2025   $250.20   $250.20   $250.20  
  Purchase #7 $52.79   8.773%   $57.4213   $57.42   $57.40   $57.40  
  7 purchase totals = $968.58       $1,061.0430   $1,061.05   $1,061.00   $1,061.00