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 $92.88   5.594%   $98.0757   $98.08   $98.10   $98.10  
  Purchase #2 $239.95   11.635%   $267.8682   $267.87   $267.85   $267.90  
  Purchase #3 $177.54   10.113%   $195.4946   $195.49   $195.50   $195.50  
  Purchase #4 $105.91   13.437%   $120.1411   $120.14   $120.15   $120.10  
  Purchase #5 $67.86   11.633%   $75.7542   $75.75   $75.75   $75.80  
  Purchase #6 $235.30   4.569%   $246.0509   $246.05   $246.05   $246.10  
  Purchase #7 $95.87   11.782%   $107.1654   $107.17   $107.15   $107.20  
  7 purchase totals = $1,015.31       $1,110.5501   $1,110.55   $1,110.55   $1,110.70