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 $76.63   12.158%   $85.9467   $85.95   $85.95   $85.90  
  Purchase #2 $24.80   7.520%   $26.665   $26.67   $26.65   $26.70  
  Purchase #3 $38.75   13.546%   $43.9991   $44.00   $44.00   $44.00  
  Purchase #4 $185.46   9.187%   $202.4982   $202.50   $202.50   $202.50  
  Purchase #5 $21.41   12.643%   $24.1169   $24.12   $24.10   $24.10  
  Purchase #6 $24.67   7.150%   $26.4339   $26.43   $26.45   $26.40  
  Purchase #7 $191.92   6.579%   $204.5464   $204.55   $204.55   $204.50  
  7 purchase totals = $563.64       $614.2062   $614.22   $614.20   $614.10