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 $195.98   8.463%   $212.5658   $212.57   $212.55   $212.60  
  Purchase #2 $235.51   11.655%   $262.9587   $262.96   $262.95   $263.00  
  Purchase #3 $180.76   8.847%   $196.7518   $196.75   $196.75   $196.80  
  Purchase #4 $225.47   3.161%   $232.5971   $232.60   $232.60   $232.60  
  Purchase #5 $35.80   13.628%   $40.6788   $40.68   $40.70   $40.70  
  Purchase #6 $40.27   7.117%   $43.136   $43.14   $43.15   $43.10  
  Purchase #7 $97.81   8.715%   $106.3341   $106.33   $106.35   $106.30  
  7 purchase totals = $1,011.60       $1,095.0223   $1,095.03   $1,095.05   $1,095.10