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 $88.86   5.299%   $93.5687   $93.57   $93.55   $93.60  
  Purchase #2 $236.51   11.601%   $263.9475   $263.95   $263.95   $263.90  
  Purchase #3 $48.82   5.434%   $51.4729   $51.47   $51.45   $51.50  
  Purchase #4 $184.67   13.256%   $209.1499   $209.15   $209.15   $209.10  
  Purchase #5 $213.40   7.719%   $229.8723   $229.87   $229.85   $229.90  
  Purchase #6 $95.45   5.714%   $100.904   $100.90   $100.90   $100.90  
  Purchase #7 $157.66   3.469%   $163.1292   $163.13   $163.15   $163.10  
  7 purchase totals = $1,025.37       $1,112.0445   $1,112.04   $1,112.00   $1,112.00