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 $49.77   9.739%   $54.6171   $54.62   $54.60   $54.60  
  Purchase #2 $161.52   4.281%   $168.4347   $168.43   $168.45   $168.40  
  Purchase #3 $128.72   4.187%   $134.1095   $134.11   $134.10   $134.10  
  Purchase #4 $232.97   8.235%   $252.1551   $252.16   $252.15   $252.20  
  Purchase #5 $62.41   3.260%   $64.4446   $64.44   $64.45   $64.40  
  Purchase #6 $198.46   4.301%   $206.9958   $207.00   $207.00   $207.00  
  Purchase #7 $192.81   10.815%   $213.6624   $213.66   $213.65   $213.70  
  7 purchase totals = $1,026.66       $1,094.4192   $1,094.42   $1,094.40   $1,094.40