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 $79.29   7.134%   $84.9465   $84.95   $84.95   $84.90  
  Purchase #2 $210.53   11.572%   $234.8925   $234.89   $234.90   $234.90  
  Purchase #3 $167.84   6.616%   $178.9443   $178.94   $178.95   $178.90  
  Purchase #4 $88.36   11.122%   $98.1874   $98.19   $98.20   $98.20  
  Purchase #5 $111.89   10.484%   $123.6205   $123.62   $123.60   $123.60  
  Purchase #6 $154.32   5.764%   $163.215   $163.22   $163.20   $163.20  
  Purchase #7 $247.64   12.678%   $279.0358   $279.04   $279.05   $279.00  
  7 purchase totals = $1,059.87       $1,162.8420   $1,162.85   $1,162.85   $1,162.70