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 $83.97   13.326%   $95.1598   $95.16   $95.15   $95.20  
  Purchase #2 $202.95   4.185%   $211.4435   $211.44   $211.45   $211.40  
  Purchase #3 $105.33   12.482%   $118.4773   $118.48   $118.50   $118.50  
  Purchase #4 $79.36   9.575%   $86.9587   $86.96   $86.95   $87.00  
  Purchase #5 $80.79   5.391%   $85.1454   $85.15   $85.15   $85.10  
  Purchase #6 $179.81   5.189%   $189.1403   $189.14   $189.15   $189.10  
  Purchase #7 $146.52   6.757%   $156.4204   $156.42   $156.40   $156.40  
  7 purchase totals = $878.73       $942.7454   $942.75   $942.75   $942.70