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 $212.53   5.379%   $223.962   $223.96   $223.95   $224.00  
  Purchase #2 $196.46   6.214%   $208.668   $208.67   $208.65   $208.70  
  Purchase #3 $172.73   5.542%   $182.3027   $182.30   $182.30   $182.30  
  Purchase #4 $90.84   12.575%   $102.2631   $102.26   $102.25   $102.30  
  Purchase #5 $219.81   3.192%   $226.8263   $226.83   $226.85   $226.80  
  Purchase #6 $217.54   4.629%   $227.6099   $227.61   $227.60   $227.60  
  Purchase #7 $123.42   10.256%   $136.078   $136.08   $136.10   $136.10  
  7 purchase totals = $1,233.33       $1,307.7100   $1,307.71   $1,307.70   $1,307.80