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 $165.33   9.688%   $181.3472   $181.35   $181.35   $181.30  
  Purchase #2 $174.84   10.786%   $193.6982   $193.70   $193.70   $193.70  
  Purchase #3 $181.26   7.850%   $195.4889   $195.49   $195.50   $195.50  
  Purchase #4 $218.75   10.531%   $241.7866   $241.79   $241.80   $241.80  
  Purchase #5 $159.35   10.656%   $176.3303   $176.33   $176.35   $176.30  
  Purchase #6 $107.93   4.270%   $112.5386   $112.54   $112.55   $112.50  
  Purchase #7 $97.30   3.397%   $100.6053   $100.61   $100.60   $100.60  
  7 purchase totals = $1,104.76       $1,201.7951   $1,201.81   $1,201.85   $1,201.70