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 $151.79   11.487%   $169.2261   $169.23   $169.25   $169.20  
  Purchase #2 $85.81   10.658%   $94.9556   $94.96   $94.95   $95.00  
  Purchase #3 $124.50   5.209%   $130.9852   $130.99   $131.00   $131.00  
  Purchase #4 $162.61   8.283%   $176.079   $176.08   $176.10   $176.10  
  Purchase #5 $205.55   11.769%   $229.7412   $229.74   $229.75   $229.70  
  Purchase #6 $169.64   5.867%   $179.5928   $179.59   $179.60   $179.60  
  Purchase #7 $168.93   10.319%   $186.3619   $186.36   $186.35   $186.40  
  7 purchase totals = $1,068.83       $1,166.9418   $1,166.95   $1,167.00   $1,167.00