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 $48.93   11.749%   $54.6788   $54.68   $54.70   $54.70  
  Purchase #2 $65.80   5.464%   $69.3953   $69.40   $69.40   $69.40  
  Purchase #3 $185.34   4.794%   $194.2252   $194.23   $194.25   $194.20  
  Purchase #4 $157.59   13.286%   $178.5274   $178.53   $178.55   $178.50  
  Purchase #5 $182.96   13.293%   $207.2809   $207.28   $207.30   $207.30  
  Purchase #6 $99.67   8.247%   $107.8898   $107.89   $107.90   $107.90  
  Purchase #7 $200.60   6.183%   $213.0031   $213.00   $213.00   $213.00  
  7 purchase totals = $940.89       $1,025.0005   $1,025.01   $1,025.10   $1,025.00