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 $162.25   7.267%   $174.0407   $174.04   $174.05   $174.00  
  Purchase #2 $189.46   9.187%   $206.8657   $206.87   $206.85   $206.90  
  Purchase #3 $16.67   3.180%   $17.2001   $17.20   $17.20   $17.20  
  Purchase #4 $98.41   9.561%   $107.819   $107.82   $107.80   $107.80  
  Purchase #5 $175.71   9.582%   $192.5465   $192.55   $192.55   $192.50  
  Purchase #6 $5.81   3.480%   $6.0122   $6.01   $6.00   $6.00  
  Purchase #7 $146.89   10.180%   $161.8434   $161.84   $161.85   $161.80  
  7 purchase totals = $795.20       $866.3276   $866.33   $866.30   $866.20