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 $87.40   10.119%   $96.244   $96.24   $96.25   $96.20  
  Purchase #2 $108.64   3.636%   $112.5902   $112.59   $112.60   $112.60  
  Purchase #3 $159.89   5.399%   $168.5225   $168.52   $168.50   $168.50  
  Purchase #4 $217.62   3.361%   $224.9342   $224.93   $224.95   $224.90  
  Purchase #5 $125.31   7.699%   $134.9576   $134.96   $134.95   $135.00  
  Purchase #6 $239.70   12.301%   $269.1855   $269.19   $269.20   $269.20  
  Purchase #7 $34.61   4.487%   $36.163   $36.16   $36.15   $36.20  
  7 purchase totals = $973.17       $1,042.5970   $1,042.59   $1,042.60   $1,042.60