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 $96.43   10.555%   $106.6082   $106.61   $106.60   $106.60  
  Purchase #2 $95.36   6.257%   $101.3267   $101.33   $101.35   $101.30  
  Purchase #3 $6.36   5.700%   $6.7225   $6.72   $6.70   $6.70  
  Purchase #4 $250.87   10.224%   $276.5189   $276.52   $276.50   $276.50  
  Purchase #5 $95.70   7.113%   $102.5071   $102.51   $102.50   $102.50  
  Purchase #6 $245.44   11.552%   $273.7932   $273.79   $273.80   $273.80  
  Purchase #7 $26.75   4.263%   $27.8904   $27.89   $27.90   $27.90  
  7 purchase totals = $816.91       $895.3670   $895.37   $895.35   $895.30