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 $191.33   8.706%   $207.9872   $207.99   $208.00   $208.00  
  Purchase #2 $133.88   8.753%   $145.5985   $145.60   $145.60   $145.60  
  Purchase #3 $148.79   9.657%   $163.1587   $163.16   $163.15   $163.20  
  Purchase #4 $164.93   11.270%   $183.5176   $183.52   $183.50   $183.50  
  Purchase #5 $131.44   5.699%   $138.9308   $138.93   $138.95   $138.90  
  Purchase #6 $73.71   11.867%   $82.4572   $82.46   $82.45   $82.50  
  Purchase #7 $208.67   11.174%   $231.9868   $231.99   $232.00   $232.00  
  7 purchase totals = $1,052.75       $1,153.6368   $1,153.65   $1,153.65   $1,153.70