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 $41.53   11.343%   $46.2407   $46.24   $46.25   $46.20  
  Purchase #2 $155.73   5.176%   $163.7906   $163.79   $163.80   $163.80  
  Purchase #3 $240.32   4.752%   $251.74   $251.74   $251.75   $251.70  
  Purchase #4 $54.37   9.475%   $59.5216   $59.52   $59.50   $59.50  
  Purchase #5 $89.90   4.163%   $93.6425   $93.64   $93.65   $93.60  
  Purchase #6 $237.57   11.165%   $264.0947   $264.09   $264.10   $264.10  
  Purchase #7 $222.97   7.673%   $240.0785   $240.08   $240.10   $240.10  
  7 purchase totals = $1,042.39       $1,119.1086   $1,119.10   $1,119.15   $1,119.00