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 $174.41   12.335%   $195.9235   $195.92   $195.90   $195.90  
  Purchase #2 $249.82   5.223%   $262.8681   $262.87   $262.85   $262.90  
  Purchase #3 $151.95   5.398%   $160.1523   $160.15   $160.15   $160.20  
  Purchase #4 $229.26   9.342%   $250.6775   $250.68   $250.70   $250.70  
  Purchase #5 $106.65   11.637%   $119.0609   $119.06   $119.05   $119.10  
  Purchase #6 $168.80   5.485%   $178.0587   $178.06   $178.05   $178.10  
  Purchase #7 $40.26   5.142%   $42.3302   $42.33   $42.35   $42.30  
  7 purchase totals = $1,121.15       $1,209.0712   $1,209.07   $1,209.05   $1,209.20