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 $195.45   3.384%   $202.064   $202.06   $202.05   $202.10  
  Purchase #2 $83.62   9.812%   $91.8248   $91.82   $91.80   $91.80  
  Purchase #3 $6.53   8.157%   $7.0627   $7.06   $7.05   $7.10  
  Purchase #4 $200.59   6.229%   $213.0848   $213.08   $213.10   $213.10  
  Purchase #5 $153.66   3.863%   $159.5959   $159.60   $159.60   $159.60  
  Purchase #6 $200.87   13.475%   $227.9372   $227.94   $227.95   $227.90  
  Purchase #7 $152.64   5.663%   $161.284   $161.28   $161.30   $161.30  
  7 purchase totals = $993.36       $1,062.8534   $1,062.84   $1,062.85   $1,062.90