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 $148.61   9.627%   $162.9167   $162.92   $162.90   $162.90  
  Purchase #2 $218.60   10.603%   $241.7782   $241.78   $241.80   $241.80  
  Purchase #3 $51.74   8.661%   $56.2212   $56.22   $56.20   $56.20  
  Purchase #4 $229.47   7.201%   $245.9941   $245.99   $246.00   $246.00  
  Purchase #5 $55.60   13.268%   $62.977   $62.98   $63.00   $63.00  
  Purchase #6 $122.65   3.408%   $126.8299   $126.83   $126.85   $126.80  
  Purchase #7 $227.69   8.617%   $247.31   $247.31   $247.30   $247.30  
  7 purchase totals = $1,054.36       $1,144.0271   $1,144.03   $1,144.05   $1,144.00