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 $186.44   5.645%   $196.9645   $196.96   $196.95   $197.00  
  Purchase #2 $119.32   4.497%   $124.6858   $124.69   $124.70   $124.70  
  Purchase #3 $150.78   6.835%   $161.0858   $161.09   $161.10   $161.10  
  Purchase #4 $63.54   10.504%   $70.2142   $70.21   $70.20   $70.20  
  Purchase #5 $244.57   7.863%   $263.8005   $263.80   $263.80   $263.80  
  Purchase #6 $152.96   4.277%   $159.5021   $159.50   $159.50   $159.50  
  Purchase #7 $42.98   7.135%   $46.0466   $46.05   $46.05   $46.00  
  7 purchase totals = $960.59       $1,022.2995   $1,022.30   $1,022.30   $1,022.30