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 $195.82   5.313%   $206.2239   $206.22   $206.20   $206.20  
  Purchase #2 $159.85   9.190%   $174.5402   $174.54   $174.55   $174.50  
  Purchase #3 $119.46   4.747%   $125.1308   $125.13   $125.15   $125.10  
  Purchase #4 $97.63   7.739%   $105.1856   $105.19   $105.20   $105.20  
  Purchase #5 $179.92   7.838%   $194.0221   $194.02   $194.00   $194.00  
  Purchase #6 $226.86   3.234%   $234.1967   $234.20   $234.20   $234.20  
  Purchase #7 $176.95   10.646%   $195.7881   $195.79   $195.80   $195.80  
  7 purchase totals = $1,156.49       $1,235.0874   $1,235.09   $1,235.10   $1,235.00