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 $105.59   4.804%   $110.6625   $110.66   $110.65   $110.70  
  Purchase #2 $242.25   8.421%   $262.6499   $262.65   $262.65   $262.60  
  Purchase #3 $40.77   9.201%   $44.5212   $44.52   $44.50   $44.50  
  Purchase #4 $250.53   9.696%   $274.8214   $274.82   $274.80   $274.80  
  Purchase #5 $199.41   8.471%   $216.302   $216.30   $216.30   $216.30  
  Purchase #6 $55.43   5.205%   $58.3151   $58.32   $58.30   $58.30  
  Purchase #7 $140.44   11.548%   $156.658   $156.66   $156.65   $156.70  
  7 purchase totals = $1,034.42       $1,123.9301   $1,123.93   $1,123.85   $1,123.90