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 $67.55   12.573%   $76.0431   $76.04   $76.05   $76.00  
  Purchase #2 $217.61   10.187%   $239.7779   $239.78   $239.80   $239.80  
  Purchase #3 $165.66   11.447%   $184.6231   $184.62   $184.60   $184.60  
  Purchase #4 $174.47   10.381%   $192.5817   $192.58   $192.60   $192.60  
  Purchase #5 $61.80   10.152%   $68.0739   $68.07   $68.05   $68.10  
  Purchase #6 $96.46   4.467%   $100.7689   $100.77   $100.75   $100.80  
  Purchase #7 $200.99   12.502%   $226.1178   $226.12   $226.10   $226.10  
  7 purchase totals = $984.54       $1,087.9864   $1,087.98   $1,087.95   $1,088.00