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 $167.68   3.858%   $174.1491   $174.15   $174.15   $174.10  
  Purchase #2 $167.47   11.618%   $186.9267   $186.93   $186.95   $186.90  
  Purchase #3 $193.87   10.587%   $214.395   $214.40   $214.40   $214.40  
  Purchase #4 $156.26   6.741%   $166.7935   $166.79   $166.80   $166.80  
  Purchase #5 $201.58   6.451%   $214.5839   $214.58   $214.60   $214.60  
  Purchase #6 $47.29   5.690%   $49.9808   $49.98   $50.00   $50.00  
  Purchase #7 $132.69   5.833%   $140.4298   $140.43   $140.45   $140.40  
  7 purchase totals = $1,066.84       $1,147.2588   $1,147.26   $1,147.35   $1,147.20