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 $66.63   11.858%   $74.531   $74.53   $74.55   $74.50  
  Purchase #2 $185.82   4.278%   $193.7694   $193.77   $193.75   $193.80  
  Purchase #3 $181.46   5.359%   $191.1844   $191.18   $191.20   $191.20  
  Purchase #4 $195.83   5.852%   $207.29   $207.29   $207.30   $207.30  
  Purchase #5 $216.29   12.783%   $243.9384   $243.94   $243.95   $243.90  
  Purchase #6 $151.26   8.307%   $163.8252   $163.83   $163.85   $163.80  
  Purchase #7 $120.89   6.665%   $128.9473   $128.95   $128.95   $128.90  
  7 purchase totals = $1,118.18       $1,203.4857   $1,203.49   $1,203.55   $1,203.40