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 $161.41   8.436%   $175.0265   $175.03   $175.05   $175.00  
  Purchase #2 $218.52   7.621%   $235.1734   $235.17   $235.15   $235.20  
  Purchase #3 $117.79   3.575%   $122.001   $122.00   $122.00   $122.00  
  Purchase #4 $137.50   11.573%   $153.4129   $153.41   $153.40   $153.40  
  Purchase #5 $245.42   12.496%   $276.0877   $276.09   $276.10   $276.10  
  Purchase #6 $73.65   10.377%   $81.2927   $81.29   $81.30   $81.30  
  Purchase #7 $178.25   7.867%   $192.2729   $192.27   $192.25   $192.30  
  7 purchase totals = $1,132.54       $1,235.2671   $1,235.26   $1,235.25   $1,235.30