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 $191.80   8.837%   $208.7494   $208.75   $208.75   $208.70  
  Purchase #2 $5.88   3.199%   $6.0681   $6.07   $6.05   $6.10  
  Purchase #3 $208.86   11.185%   $232.221   $232.22   $232.20   $232.20  
  Purchase #4 $224.91   6.225%   $238.9106   $238.91   $238.90   $238.90  
  Purchase #5 $143.74   3.691%   $149.0454   $149.05   $149.05   $149.00  
  Purchase #6 $59.80   8.678%   $64.9894   $64.99   $65.00   $65.00  
  Purchase #7 $245.90   3.131%   $253.5991   $253.60   $253.60   $253.60  
  7 purchase totals = $1,080.89       $1,153.5830   $1,153.59   $1,153.55   $1,153.50