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 $162.91   8.152%   $176.1904   $176.19   $176.20   $176.20  
  Purchase #2 $244.33   9.129%   $266.6349   $266.63   $266.65   $266.60  
  Purchase #3 $131.54   4.604%   $137.5961   $137.60   $137.60   $137.60  
  Purchase #4 $75.45   12.178%   $84.6383   $84.64   $84.65   $84.60  
  Purchase #5 $184.96   8.849%   $201.3271   $201.33   $201.35   $201.30  
  Purchase #6 $12.56   6.143%   $13.3316   $13.33   $13.35   $13.30  
  Purchase #7 $202.76   10.638%   $224.3296   $224.33   $224.35   $224.30  
  7 purchase totals = $1,014.51       $1,104.0480   $1,104.05   $1,104.15   $1,103.90