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 $151.26   12.154%   $169.6441   $169.64   $169.65   $169.60  
  Purchase #2 $195.53   10.144%   $215.3646   $215.36   $215.35   $215.40  
  Purchase #3 $61.42   4.118%   $63.9493   $63.95   $63.95   $63.90  
  Purchase #4 $17.88   6.694%   $19.0769   $19.08   $19.10   $19.10  
  Purchase #5 $249.30   6.497%   $265.497   $265.50   $265.50   $265.50  
  Purchase #6 $216.52   5.864%   $229.2167   $229.22   $229.20   $229.20  
  Purchase #7 $227.86   3.139%   $235.0125   $235.01   $235.00   $235.00  
  7 purchase totals = $1,119.77       $1,197.7611   $1,197.76   $1,197.75   $1,197.70