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 $55.85   9.391%   $61.0949   $61.09   $61.10   $61.10  
  Purchase #2 $213.58   7.338%   $229.2525   $229.25   $229.25   $229.30  
  Purchase #3 $59.81   8.683%   $65.0033   $65.00   $65.00   $65.00  
  Purchase #4 $241.55   9.254%   $263.903   $263.90   $263.90   $263.90  
  Purchase #5 $209.35   11.663%   $233.7665   $233.77   $233.75   $233.80  
  Purchase #6 $186.91   5.565%   $197.3115   $197.31   $197.30   $197.30  
  Purchase #7 $165.90   6.818%   $177.2111   $177.21   $177.20   $177.20  
  7 purchase totals = $1,132.95       $1,227.5428   $1,227.53   $1,227.50   $1,227.60