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 $67.66   9.370%   $73.9997   $74.00   $74.00   $74.00  
  Purchase #2 $167.74   6.852%   $179.2335   $179.23   $179.25   $179.20  
  Purchase #3 $200.37   5.194%   $210.7772   $210.78   $210.80   $210.80  
  Purchase #4 $67.93   13.642%   $77.197   $77.20   $77.20   $77.20  
  Purchase #5 $133.31   3.280%   $137.6826   $137.68   $137.70   $137.70  
  Purchase #6 $28.77   6.465%   $30.63   $30.63   $30.65   $30.60  
  Purchase #7 $231.34   5.160%   $243.2771   $243.28   $243.30   $243.30  
  7 purchase totals = $897.12       $952.7971   $952.80   $952.90   $952.80