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 $243.84   10.707%   $269.9479   $269.95   $269.95   $269.90  
  Purchase #2 $154.96   5.358%   $163.2628   $163.26   $163.25   $163.30  
  Purchase #3 $63.76   12.322%   $71.6165   $71.62   $71.60   $71.60  
  Purchase #4 $148.84   11.749%   $166.3272   $166.33   $166.35   $166.30  
  Purchase #5 $106.86   13.669%   $121.4667   $121.47   $121.45   $121.50  
  Purchase #6 $221.94   10.805%   $245.9206   $245.92   $245.90   $245.90  
  Purchase #7 $116.36   6.350%   $123.7489   $123.75   $123.75   $123.70  
  7 purchase totals = $1,056.56       $1,162.2906   $1,162.30   $1,162.25   $1,162.20