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 $211.79   9.839%   $232.628   $232.63   $232.65   $232.60  
  Purchase #2 $231.33   9.492%   $253.2878   $253.29   $253.30   $253.30  
  Purchase #3 $117.91   12.852%   $133.0638   $133.06   $133.05   $133.10  
  Purchase #4 $88.82   10.468%   $98.1177   $98.12   $98.10   $98.10  
  Purchase #5 $161.65   8.149%   $174.8229   $174.82   $174.80   $174.80  
  Purchase #6 $243.78   8.376%   $264.199   $264.20   $264.20   $264.20  
  Purchase #7 $172.35   3.477%   $178.3426   $178.34   $178.35   $178.30  
  7 purchase totals = $1,227.63       $1,334.4618   $1,334.46   $1,334.45   $1,334.40