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 $95.78   11.649%   $106.9374   $106.94   $106.95   $106.90  
  Purchase #2 $88.81   4.298%   $92.6271   $92.63   $92.65   $92.60  
  Purchase #3 $44.69   7.363%   $47.9805   $47.98   $48.00   $48.00  
  Purchase #4 $161.33   13.556%   $183.1999   $183.20   $183.20   $183.20  
  Purchase #5 $89.68   8.357%   $97.1746   $97.17   $97.15   $97.20  
  Purchase #6 $241.77   6.396%   $257.2336   $257.23   $257.25   $257.20  
  Purchase #7 $45.45   10.455%   $50.2018   $50.20   $50.20   $50.20  
  7 purchase totals = $767.51       $835.3549   $835.35   $835.40   $835.30