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 $36.85   13.213%   $41.719   $41.72   $41.70   $41.70  
  Purchase #2 $108.51   5.394%   $114.363   $114.36   $114.35   $114.40  
  Purchase #3 $166.86   4.139%   $173.7663   $173.77   $173.75   $173.80  
  Purchase #4 $233.50   9.632%   $255.9907   $255.99   $256.00   $256.00  
  Purchase #5 $95.89   10.549%   $106.0054   $106.01   $106.00   $106.00  
  Purchase #6 $231.54   11.243%   $257.572   $257.57   $257.55   $257.60  
  Purchase #7 $213.69   4.722%   $223.7804   $223.78   $223.80   $223.80  
  7 purchase totals = $1,086.84       $1,173.1968   $1,173.20   $1,173.15   $1,173.30