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 $89.37   6.249%   $94.9547   $94.95   $94.95   $95.00  
  Purchase #2 $48.33   4.624%   $50.5648   $50.56   $50.55   $50.60  
  Purchase #3 $243.75   3.302%   $251.7986   $251.80   $251.80   $251.80  
  Purchase #4 $58.75   12.219%   $65.9287   $65.93   $65.95   $65.90  
  Purchase #5 $186.89   6.782%   $199.5649   $199.56   $199.55   $199.60  
  Purchase #6 $238.97   4.567%   $249.8838   $249.88   $249.90   $249.90  
  Purchase #7 $175.73   6.105%   $186.4583   $186.46   $186.45   $186.50  
  7 purchase totals = $1,041.79       $1,099.1538   $1,099.14   $1,099.15   $1,099.30