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 $247.97   11.569%   $276.6576   $276.66   $276.65   $276.70  
  Purchase #2 $212.95   9.505%   $233.1909   $233.19   $233.20   $233.20  
  Purchase #3 $51.28   9.186%   $55.9906   $55.99   $56.00   $56.00  
  Purchase #4 $164.62   4.361%   $171.7991   $171.80   $171.80   $171.80  
  Purchase #5 $110.36   4.334%   $115.143   $115.14   $115.15   $115.10  
  Purchase #6 $55.83   9.742%   $61.269   $61.27   $61.25   $61.30  
  Purchase #7 $124.92   4.788%   $130.9012   $130.90   $130.90   $130.90  
  7 purchase totals = $967.93       $1,044.9514   $1,044.95   $1,044.95   $1,045.00