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 $118.63   10.303%   $130.8524   $130.85   $130.85   $130.90  
  Purchase #2 $189.75   11.546%   $211.6585   $211.66   $211.65   $211.70  
  Purchase #3 $22.71   6.714%   $24.2347   $24.23   $24.25   $24.20  
  Purchase #4 $162.69   11.339%   $181.1374   $181.14   $181.15   $181.10  
  Purchase #5 $15.52   5.834%   $16.4254   $16.43   $16.45   $16.40  
  Purchase #6 $197.87   8.559%   $214.8057   $214.81   $214.80   $214.80  
  Purchase #7 $248.52   10.530%   $274.6892   $274.69   $274.70   $274.70  
  7 purchase totals = $955.69       $1,053.8033   $1,053.81   $1,053.85   $1,053.80