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 $57.78   7.822%   $62.2996   $62.30   $62.30   $62.30  
  Purchase #2 $33.53   4.472%   $35.0295   $35.03   $35.05   $35.00  
  Purchase #3 $245.26   9.693%   $269.0331   $269.03   $269.05   $269.00  
  Purchase #4 $247.46   4.104%   $257.6158   $257.62   $257.60   $257.60  
  Purchase #5 $65.62   13.180%   $74.2687   $74.27   $74.25   $74.30  
  Purchase #6 $49.93   9.706%   $54.7762   $54.78   $54.80   $54.80  
  Purchase #7 $112.27   6.269%   $119.3082   $119.31   $119.30   $119.30  
  7 purchase totals = $811.85       $872.3311   $872.34   $872.35   $872.30