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 $116.27   7.732%   $125.26   $125.26   $125.25   $125.30  
  Purchase #2 $231.41   3.550%   $239.6251   $239.63   $239.65   $239.60  
  Purchase #3 $88.80   10.411%   $98.045   $98.05   $98.05   $98.00  
  Purchase #4 $58.69   4.383%   $61.2624   $61.26   $61.25   $61.30  
  Purchase #5 $203.83   4.109%   $212.2054   $212.21   $212.20   $212.20  
  Purchase #6 $232.50   9.257%   $254.0225   $254.02   $254.00   $254.00  
  Purchase #7 $163.46   3.173%   $168.6466   $168.65   $168.65   $168.60  
  7 purchase totals = $1,094.96       $1,159.0670   $1,159.08   $1,159.05   $1,159.00