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 $12.63   10.838%   $13.9988   $14.00   $14.00   $14.00  
  Purchase #2 $164.42   13.504%   $186.6233   $186.62   $186.60   $186.60  
  Purchase #3 $150.82   3.656%   $156.334   $156.33   $156.35   $156.30  
  Purchase #4 $243.60   9.421%   $266.5496   $266.55   $266.55   $266.50  
  Purchase #5 $231.51   5.239%   $243.6388   $243.64   $243.65   $243.60  
  Purchase #6 $112.79   13.548%   $128.0708   $128.07   $128.05   $128.10  
  Purchase #7 $181.59   5.544%   $191.6573   $191.66   $191.65   $191.70  
  7 purchase totals = $1,097.36       $1,186.8726   $1,186.87   $1,186.85   $1,186.80