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 $195.87   4.636%   $204.9505   $204.95   $204.95   $205.00  
  Purchase #2 $66.90   7.106%   $71.6539   $71.65   $71.65   $71.70  
  Purchase #3 $234.48   7.378%   $251.7799   $251.78   $251.80   $251.80  
  Purchase #4 $62.25   5.784%   $65.8505   $65.85   $65.85   $65.90  
  Purchase #5 $224.76   11.178%   $249.8837   $249.88   $249.90   $249.90  
  Purchase #6 $145.78   3.801%   $151.3211   $151.32   $151.30   $151.30  
  Purchase #7 $182.40   8.438%   $197.7909   $197.79   $197.80   $197.80  
  7 purchase totals = $1,112.44       $1,193.2305   $1,193.22   $1,193.25   $1,193.40