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 $82.37   5.188%   $86.6434   $86.64   $86.65   $86.60  
  Purchase #2 $98.72   8.635%   $107.2445   $107.24   $107.25   $107.20  
  Purchase #3 $147.68   5.770%   $156.2011   $156.20   $156.20   $156.20  
  Purchase #4 $24.50   5.204%   $25.775   $25.78   $25.80   $25.80  
  Purchase #5 $200.60   4.486%   $209.5989   $209.60   $209.60   $209.60  
  Purchase #6 $163.39   5.478%   $172.3405   $172.34   $172.35   $172.30  
  Purchase #7 $181.72   6.137%   $192.8722   $192.87   $192.85   $192.90  
  7 purchase totals = $898.98       $950.6756   $950.67   $950.70   $950.60