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 $58.42   9.395%   $63.9086   $63.91   $63.90   $63.90  
  Purchase #2 $118.75   11.261%   $132.1224   $132.12   $132.10   $132.10  
  Purchase #3 $16.50   9.487%   $18.0654   $18.07   $18.05   $18.10  
  Purchase #4 $79.78   6.655%   $85.0894   $85.09   $85.10   $85.10  
  Purchase #5 $98.65   8.405%   $106.9415   $106.94   $106.95   $106.90  
  Purchase #6 $205.45   12.184%   $230.482   $230.48   $230.50   $230.50  
  Purchase #7 $214.42   11.557%   $239.2005   $239.20   $239.20   $239.20  
  7 purchase totals = $791.97       $875.8098   $875.81   $875.80   $875.80