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 $91.44   3.846%   $94.9568   $94.96   $94.95   $95.00  
  Purchase #2 $221.95   13.617%   $252.1729   $252.17   $252.15   $252.20  
  Purchase #3 $244.51   7.505%   $262.8605   $262.86   $262.85   $262.90  
  Purchase #4 $227.30   10.430%   $251.0074   $251.01   $251.00   $251.00  
  Purchase #5 $136.55   4.560%   $142.7767   $142.78   $142.80   $142.80  
  Purchase #6 $17.63   12.857%   $19.8967   $19.90   $19.90   $19.90  
  Purchase #7 $123.91   8.383%   $134.2974   $134.30   $134.30   $134.30  
  7 purchase totals = $1,063.29       $1,157.9684   $1,157.98   $1,157.95   $1,158.10