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 $85.25   11.455%   $95.0154   $95.02   $95.00   $95.00  
  Purchase #2 $229.83   7.432%   $246.911   $246.91   $246.90   $246.90  
  Purchase #3 $176.96   11.827%   $197.8891   $197.89   $197.90   $197.90  
  Purchase #4 $40.37   4.790%   $42.3037   $42.30   $42.30   $42.30  
  Purchase #5 $191.77   6.519%   $204.2715   $204.27   $204.25   $204.30  
  Purchase #6 $248.69   3.652%   $257.7722   $257.77   $257.75   $257.80  
  Purchase #7 $12.86   11.653%   $14.3586   $14.36   $14.35   $14.40  
  7 purchase totals = $985.73       $1,058.5215   $1,058.52   $1,058.45   $1,058.60