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 $53.56   5.872%   $56.705   $56.71   $56.70   $56.70  
  Purchase #2 $194.69   4.239%   $202.9429   $202.94   $202.95   $202.90  
  Purchase #3 $69.59   3.107%   $71.7522   $71.75   $71.75   $71.80  
  Purchase #4 $216.82   8.119%   $234.4236   $234.42   $234.40   $234.40  
  Purchase #5 $126.73   12.587%   $142.6815   $142.68   $142.70   $142.70  
  Purchase #6 $227.33   9.371%   $248.6331   $248.63   $248.65   $248.60  
  Purchase #7 $194.53   4.346%   $202.9843   $202.98   $203.00   $203.00  
  7 purchase totals = $1,083.25       $1,160.1226   $1,160.11   $1,160.15   $1,160.10