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 $95.67   12.517%   $107.645   $107.65   $107.65   $107.60  
  Purchase #2 $248.94   5.317%   $262.1761   $262.18   $262.20   $262.20  
  Purchase #3 $67.85   10.144%   $74.7327   $74.73   $74.75   $74.70  
  Purchase #4 $215.26   10.381%   $237.6061   $237.61   $237.60   $237.60  
  Purchase #5 $142.97   6.525%   $152.2988   $152.30   $152.30   $152.30  
  Purchase #6 $65.76   4.197%   $68.5199   $68.52   $68.50   $68.50  
  Purchase #7 $68.42   5.767%   $72.3658   $72.37   $72.35   $72.40  
  7 purchase totals = $904.87       $975.3444   $975.36   $975.35   $975.30