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 $59.36   4.854%   $62.2413   $62.24   $62.25   $62.20  
  Purchase #2 $114.52   8.685%   $124.4661   $124.47   $124.45   $124.50  
  Purchase #3 $18.83   5.295%   $19.827   $19.83   $19.85   $19.80  
  Purchase #4 $8.29   11.844%   $9.2719   $9.27   $9.25   $9.30  
  Purchase #5 $222.44   12.222%   $249.6266   $249.63   $249.65   $249.60  
  Purchase #6 $233.52   4.703%   $244.5024   $244.50   $244.50   $244.50  
  Purchase #7 $23.44   6.312%   $24.9195   $24.92   $24.90   $24.90  
  7 purchase totals = $680.40       $734.8548   $734.86   $734.85   $734.80