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 $174.68   13.778%   $198.7474   $198.75   $198.75   $198.70  
  Purchase #2 $66.43   10.139%   $73.1653   $73.17   $73.15   $73.20  
  Purchase #3 $56.51   8.852%   $61.5123   $61.51   $61.50   $61.50  
  Purchase #4 $245.97   13.170%   $278.3642   $278.36   $278.35   $278.40  
  Purchase #5 $73.35   4.107%   $76.3625   $76.36   $76.35   $76.40  
  Purchase #6 $9.41   5.813%   $9.957   $9.96   $9.95   $10.00  
  Purchase #7 $58.82   5.349%   $61.9663   $61.97   $61.95   $62.00  
  7 purchase totals = $685.17       $760.0750   $760.08   $760.00   $760.20