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 $172.73   13.274%   $195.6582   $195.66   $195.65   $195.70  
  Purchase #2 $245.77   7.358%   $263.8538   $263.85   $263.85   $263.90  
  Purchase #3 $170.89   8.609%   $185.6019   $185.60   $185.60   $185.60  
  Purchase #4 $227.94   11.357%   $253.8271   $253.83   $253.85   $253.80  
  Purchase #5 $106.69   11.405%   $118.858   $118.86   $118.85   $118.90  
  Purchase #6 $36.30   3.605%   $37.6086   $37.61   $37.60   $37.60  
  Purchase #7 $159.97   10.816%   $177.2724   $177.27   $177.25   $177.30  
  7 purchase totals = $1,120.29       $1,232.6800   $1,232.68   $1,232.65   $1,232.80