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 $73.84   6.491%   $78.633   $78.63   $78.65   $78.60  
  Purchase #2 $238.65   9.638%   $261.6511   $261.65   $261.65   $261.70  
  Purchase #3 $95.31   12.501%   $107.2247   $107.22   $107.20   $107.20  
  Purchase #4 $198.41   12.436%   $223.0843   $223.08   $223.10   $223.10  
  Purchase #5 $95.67   9.707%   $104.9567   $104.96   $104.95   $105.00  
  Purchase #6 $162.95   3.459%   $168.5864   $168.59   $168.60   $168.60  
  Purchase #7 $217.79   5.501%   $229.7706   $229.77   $229.75   $229.80  
  7 purchase totals = $1,082.62       $1,173.9068   $1,173.90   $1,173.90   $1,174.00