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 $62.87   11.262%   $69.9504   $69.95   $69.95   $70.00  
  Purchase #2 $111.33   10.223%   $122.7113   $122.71   $122.70   $122.70  
  Purchase #3 $59.93   6.627%   $63.9016   $63.90   $63.90   $63.90  
  Purchase #4 $158.71   4.147%   $165.2917   $165.29   $165.30   $165.30  
  Purchase #5 $160.90   7.223%   $172.5218   $172.52   $172.50   $172.50  
  Purchase #6 $44.94   8.644%   $48.8246   $48.82   $48.80   $48.80  
  Purchase #7 $116.80   10.257%   $128.7802   $128.78   $128.80   $128.80  
  7 purchase totals = $715.48       $771.9816   $771.97   $771.95   $772.00