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 $71.49   6.498%   $76.1354   $76.14   $76.15   $76.10  
  Purchase #2 $65.92   9.258%   $72.0229   $72.02   $72.00   $72.00  
  Purchase #3 $191.36   5.427%   $201.7451   $201.75   $201.75   $201.70  
  Purchase #4 $222.34   9.776%   $244.076   $244.08   $244.10   $244.10  
  Purchase #5 $152.99   6.796%   $163.3872   $163.39   $163.40   $163.40  
  Purchase #6 $188.68   11.418%   $210.2235   $210.22   $210.20   $210.20  
  Purchase #7 $243.76   10.439%   $269.2061   $269.21   $269.20   $269.20  
  7 purchase totals = $1,136.54       $1,236.7962   $1,236.81   $1,236.80   $1,236.70