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 $112.68   5.642%   $119.0374   $119.04   $119.05   $119.00  
  Purchase #2 $95.33   11.245%   $106.0499   $106.05   $106.05   $106.00  
  Purchase #3 $14.32   13.126%   $16.1996   $16.20   $16.20   $16.20  
  Purchase #4 $168.96   13.451%   $191.6868   $191.69   $191.70   $191.70  
  Purchase #5 $165.55   9.789%   $181.7557   $181.76   $181.75   $181.80  
  Purchase #6 $143.60   7.639%   $154.5696   $154.57   $154.55   $154.60  
  Purchase #7 $29.80   7.872%   $32.1459   $32.15   $32.15   $32.10  
  7 purchase totals = $730.24       $801.4449   $801.46   $801.45   $801.40