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 $212.59   11.615%   $237.2823   $237.28   $237.30   $237.30  
  Purchase #2 $105.89   4.534%   $110.6911   $110.69   $110.70   $110.70  
  Purchase #3 $219.37   4.467%   $229.1693   $229.17   $229.15   $229.20  
  Purchase #4 $214.95   4.569%   $224.7711   $224.77   $224.75   $224.80  
  Purchase #5 $41.92   8.512%   $45.4882   $45.49   $45.50   $45.50  
  Purchase #6 $225.55   3.680%   $233.8502   $233.85   $233.85   $233.90  
  Purchase #7 $56.28   8.230%   $60.9118   $60.91   $60.90   $60.90  
  7 purchase totals = $1,076.55       $1,142.1640   $1,142.16   $1,142.15   $1,142.30