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 $63.77   7.807%   $68.7485   $68.75   $68.75   $68.70  
  Purchase #2 $229.31   13.594%   $260.4824   $260.48   $260.50   $260.50  
  Purchase #3 $191.30   11.152%   $212.6338   $212.63   $212.65   $212.60  
  Purchase #4 $147.74   5.797%   $156.3045   $156.30   $156.30   $156.30  
  Purchase #5 $132.97   10.236%   $146.5808   $146.58   $146.60   $146.60  
  Purchase #6 $114.66   7.438%   $123.1884   $123.19   $123.20   $123.20  
  Purchase #7 $86.60   6.393%   $92.1363   $92.14   $92.15   $92.10  
  7 purchase totals = $966.35       $1,060.0747   $1,060.07   $1,060.15   $1,060.00