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 $116.30   8.331%   $125.989   $125.99   $126.00   $126.00  
  Purchase #2 $22.67   8.704%   $24.6432   $24.64   $24.65   $24.60  
  Purchase #3 $121.79   4.660%   $127.4654   $127.47   $127.45   $127.50  
  Purchase #4 $246.55   8.437%   $267.3514   $267.35   $267.35   $267.40  
  Purchase #5 $207.47   9.255%   $226.6713   $226.67   $226.65   $226.70  
  Purchase #6 $236.33   13.861%   $269.0877   $269.09   $269.10   $269.10  
  Purchase #7 $94.46   8.436%   $102.4286   $102.43   $102.45   $102.40  
  7 purchase totals = $1,045.57       $1,143.6366   $1,143.64   $1,143.65   $1,143.70