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 $9.50   11.725%   $10.6139   $10.61   $10.60   $10.60  
  Purchase #2 $113.98   8.658%   $123.8484   $123.85   $123.85   $123.80  
  Purchase #3 $110.58   4.793%   $115.8801   $115.88   $115.90   $115.90  
  Purchase #4 $232.87   4.677%   $243.7613   $243.76   $243.75   $243.80  
  Purchase #5 $146.67   13.262%   $166.1214   $166.12   $166.10   $166.10  
  Purchase #6 $5.84   7.454%   $6.2753   $6.28   $6.30   $6.30  
  Purchase #7 $84.78   8.456%   $91.949   $91.95   $91.95   $91.90  
  7 purchase totals = $704.22       $758.4494   $758.45   $758.45   $758.40