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 $212.30   7.204%   $227.5941   $227.59   $227.60   $227.60  
  Purchase #2 $153.36   5.423%   $161.6767   $161.68   $161.70   $161.70  
  Purchase #3 $151.31   13.873%   $172.3012   $172.30   $172.30   $172.30  
  Purchase #4 $208.34   3.428%   $215.4819   $215.48   $215.50   $215.50  
  Purchase #5 $151.96   5.688%   $160.6035   $160.60   $160.60   $160.60  
  Purchase #6 $166.27   12.198%   $186.5516   $186.55   $186.55   $186.60  
  Purchase #7 $10.95   6.671%   $11.6805   $11.68   $11.70   $11.70  
  7 purchase totals = $1,054.49       $1,135.8895   $1,135.88   $1,135.95   $1,136.00