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 $26.66   7.322%   $28.612   $28.61   $28.60   $28.60  
  Purchase #2 $87.73   10.285%   $96.753   $96.75   $96.75   $96.80  
  Purchase #3 $69.30   7.320%   $74.3728   $74.37   $74.35   $74.40  
  Purchase #4 $204.50   4.349%   $213.3937   $213.39   $213.40   $213.40  
  Purchase #5 $119.65   6.428%   $127.3411   $127.34   $127.35   $127.30  
  Purchase #6 $208.55   4.469%   $217.8701   $217.87   $217.85   $217.90  
  Purchase #7 $235.56   5.147%   $247.6843   $247.68   $247.70   $247.70  
  7 purchase totals = $951.95       $1,006.0270   $1,006.01   $1,006.00   $1,006.10