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 $95.68   5.525%   $100.9663   $100.97   $100.95   $101.00  
  Purchase #2 $52.63   11.363%   $58.6103   $58.61   $58.60   $58.60  
  Purchase #3 $7.62   12.809%   $8.596   $8.60   $8.60   $8.60  
  Purchase #4 $12.52   3.657%   $12.9779   $12.98   $13.00   $13.00  
  Purchase #5 $54.99   11.151%   $61.1219   $61.12   $61.10   $61.10  
  Purchase #6 $22.69   8.859%   $24.7001   $24.70   $24.70   $24.70  
  Purchase #7 $110.88   7.577%   $119.2814   $119.28   $119.30   $119.30  
  7 purchase totals = $357.01       $386.2539   $386.26   $386.25   $386.30