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 $176.27   10.375%   $194.558   $194.56   $194.55   $194.60  
  Purchase #2 $234.92   8.509%   $254.9093   $254.91   $254.90   $254.90  
  Purchase #3 $193.26   12.298%   $217.0271   $217.03   $217.05   $217.00  
  Purchase #4 $93.77   9.848%   $103.0045   $103.00   $103.00   $103.00  
  Purchase #5 $172.91   13.122%   $195.5993   $195.60   $195.60   $195.60  
  Purchase #6 $31.99   11.459%   $35.6557   $35.66   $35.65   $35.70  
  Purchase #7 $193.65   4.316%   $202.0079   $202.01   $202.00   $202.00  
  7 purchase totals = $1,096.77       $1,202.7618   $1,202.77   $1,202.75   $1,202.80