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 $41.90   10.740%   $46.4001   $46.40   $46.40   $46.40  
  Purchase #2 $238.78   11.419%   $266.0463   $266.05   $266.05   $266.00  
  Purchase #3 $199.44   8.621%   $216.6337   $216.63   $216.65   $216.60  
  Purchase #4 $243.52   7.485%   $261.7475   $261.75   $261.75   $261.70  
  Purchase #5 $155.37   12.232%   $174.3749   $174.37   $174.35   $174.40  
  Purchase #6 $112.79   11.769%   $126.0643   $126.06   $126.05   $126.10  
  Purchase #7 $22.87   5.785%   $24.193   $24.19   $24.20   $24.20  
  7 purchase totals = $1,014.67       $1,115.4598   $1,115.45   $1,115.45   $1,115.40