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 $56.83   9.109%   $62.0066   $62.01   $62.00   $62.00  
  Purchase #2 $196.71   9.122%   $214.6539   $214.65   $214.65   $214.70  
  Purchase #3 $160.71   7.850%   $173.3257   $173.33   $173.35   $173.30  
  Purchase #4 $84.60   8.119%   $91.4687   $91.47   $91.45   $91.50  
  Purchase #5 $199.36   12.654%   $224.587   $224.59   $224.60   $224.60  
  Purchase #6 $134.68   12.325%   $151.2793   $151.28   $151.30   $151.30  
  Purchase #7 $100.60   13.300%   $113.9798   $113.98   $114.00   $114.00  
  7 purchase totals = $933.49       $1,031.3010   $1,031.31   $1,031.35   $1,031.40