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 $67.61   10.555%   $74.7462   $74.75   $74.75   $74.70  
  Purchase #2 $185.94   3.540%   $192.5223   $192.52   $192.50   $192.50  
  Purchase #3 $79.61   4.213%   $82.964   $82.96   $82.95   $83.00  
  Purchase #4 $117.57   7.161%   $125.9892   $125.99   $126.00   $126.00  
  Purchase #5 $179.89   10.145%   $198.1398   $198.14   $198.15   $198.10  
  Purchase #6 $241.28   4.226%   $251.4765   $251.48   $251.50   $251.50  
  Purchase #7 $67.89   11.162%   $75.4679   $75.47   $75.45   $75.50  
  7 purchase totals = $939.79       $1,001.3059   $1,001.31   $1,001.30   $1,001.30