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 $226.27   3.872%   $235.0312   $235.03   $235.05   $235.00  
  Purchase #2 $184.57   13.840%   $210.1145   $210.11   $210.10   $210.10  
  Purchase #3 $53.54   12.599%   $60.2855   $60.29   $60.30   $60.30  
  Purchase #4 $211.59   3.397%   $218.7777   $218.78   $218.80   $218.80  
  Purchase #5 $147.90   10.520%   $163.4591   $163.46   $163.45   $163.50  
  Purchase #6 $231.28   4.400%   $241.4563   $241.46   $241.45   $241.50  
  Purchase #7 $33.80   5.702%   $35.7273   $35.73   $35.75   $35.70  
  7 purchase totals = $1,088.95       $1,164.8516   $1,164.86   $1,164.90   $1,164.90