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 $224.70   7.506%   $241.566   $241.57   $241.55   $241.60  
  Purchase #2 $65.61   10.616%   $72.5752   $72.58   $72.60   $72.60  
  Purchase #3 $241.43   8.709%   $262.4561   $262.46   $262.45   $262.50  
  Purchase #4 $122.68   3.763%   $127.2964   $127.30   $127.30   $127.30  
  Purchase #5 $207.25   6.598%   $220.9244   $220.92   $220.90   $220.90  
  Purchase #6 $136.52   12.769%   $153.9522   $153.95   $153.95   $154.00  
  Purchase #7 $126.76   10.600%   $140.1966   $140.20   $140.20   $140.20  
  7 purchase totals = $1,124.95       $1,218.9669   $1,218.98   $1,218.95   $1,219.10