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 $86.36   10.287%   $95.2439   $95.24   $95.25   $95.20  
  Purchase #2 $98.52   4.515%   $102.9682   $102.97   $102.95   $103.00  
  Purchase #3 $223.67   3.525%   $231.5544   $231.55   $231.55   $231.60  
  Purchase #4 $186.87   7.603%   $201.0777   $201.08   $201.10   $201.10  
  Purchase #5 $147.63   10.541%   $163.1917   $163.19   $163.20   $163.20  
  Purchase #6 $235.44   4.352%   $245.6863   $245.69   $245.70   $245.70  
  Purchase #7 $45.76   11.510%   $51.027   $51.03   $51.05   $51.00  
  7 purchase totals = $1,024.25       $1,090.7492   $1,090.75   $1,090.80   $1,090.80