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 $208.60   7.833%   $224.9396   $224.94   $224.95   $224.90  
  Purchase #2 $158.62   7.856%   $171.0812   $171.08   $171.10   $171.10  
  Purchase #3 $222.62   8.476%   $241.4893   $241.49   $241.50   $241.50  
  Purchase #4 $55.96   8.627%   $60.7877   $60.79   $60.80   $60.80  
  Purchase #5 $116.70   12.169%   $130.9012   $130.90   $130.90   $130.90  
  Purchase #6 $164.95   10.847%   $182.8421   $182.84   $182.85   $182.80  
  Purchase #7 $22.74   13.190%   $25.7394   $25.74   $25.75   $25.70  
  7 purchase totals = $950.19       $1,037.7805   $1,037.78   $1,037.85   $1,037.70