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 $96.69   9.696%   $106.0651   $106.07   $106.05   $106.10  
  Purchase #2 $225.93   4.338%   $235.7308   $235.73   $235.75   $235.70  
  Purchase #3 $154.32   4.395%   $161.1024   $161.10   $161.10   $161.10  
  Purchase #4 $210.95   7.114%   $225.957   $225.96   $225.95   $226.00  
  Purchase #5 $148.57   11.682%   $165.9259   $165.93   $165.95   $165.90  
  Purchase #6 $235.46   13.438%   $267.1011   $267.10   $267.10   $267.10  
  Purchase #7 $54.79   5.752%   $57.9415   $57.94   $57.95   $57.90  
  7 purchase totals = $1,126.71       $1,219.8238   $1,219.83   $1,219.85   $1,219.80