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 $59.39   4.808%   $62.2455   $62.25   $62.25   $62.20  
  Purchase #2 $202.91   8.260%   $219.6704   $219.67   $219.65   $219.70  
  Purchase #3 $150.91   4.145%   $157.1652   $157.17   $157.15   $157.20  
  Purchase #4 $118.64   13.451%   $134.5983   $134.60   $134.60   $134.60  
  Purchase #5 $101.36   5.684%   $107.1213   $107.12   $107.10   $107.10  
  Purchase #6 $102.52   8.473%   $111.2065   $111.21   $111.20   $111.20  
  Purchase #7 $178.87   5.437%   $188.5952   $188.60   $188.60   $188.60  
  7 purchase totals = $914.60       $980.6024   $980.62   $980.55   $980.60