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 $62.26   4.665%   $65.1644   $65.16   $65.15   $65.20  
  Purchase #2 $207.80   4.863%   $217.9053   $217.91   $217.90   $217.90  
  Purchase #3 $70.66   7.313%   $75.8274   $75.83   $75.85   $75.80  
  Purchase #4 $223.61   10.694%   $247.5229   $247.52   $247.50   $247.50  
  Purchase #5 $120.87   5.143%   $127.0863   $127.09   $127.10   $127.10  
  Purchase #6 $10.74   11.453%   $11.9701   $11.97   $11.95   $12.00  
  Purchase #7 $59.90   10.115%   $65.9589   $65.96   $65.95   $66.00  
  7 purchase totals = $755.84       $811.4353   $811.44   $811.40   $811.50