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 $167.38   5.421%   $176.4537   $176.45   $176.45   $176.50  
  Purchase #2 $197.64   6.794%   $211.0677   $211.07   $211.05   $211.10  
  Purchase #3 $62.29   9.626%   $68.286   $68.29   $68.30   $68.30  
  Purchase #4 $104.97   4.863%   $110.0747   $110.07   $110.05   $110.10  
  Purchase #5 $241.53   6.195%   $256.4928   $256.49   $256.50   $256.50  
  Purchase #6 $179.85   11.198%   $199.9896   $199.99   $200.00   $200.00  
  Purchase #7 $201.34   6.267%   $213.958   $213.96   $213.95   $214.00  
  7 purchase totals = $1,155.00       $1,236.3225   $1,236.32   $1,236.30   $1,236.50