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 $86.72   9.502%   $94.9601   $94.96   $94.95   $95.00  
  Purchase #2 $11.81   9.271%   $12.9049   $12.90   $12.90   $12.90  
  Purchase #3 $207.78   3.523%   $215.1001   $215.10   $215.10   $215.10  
  Purchase #4 $191.94   7.179%   $205.7194   $205.72   $205.70   $205.70  
  Purchase #5 $97.65   9.170%   $106.6045   $106.60   $106.60   $106.60  
  Purchase #6 $145.40   8.866%   $158.2912   $158.29   $158.30   $158.30  
  Purchase #7 $244.52   5.196%   $257.2253   $257.23   $257.25   $257.20  
  7 purchase totals = $985.82       $1,050.8055   $1,050.80   $1,050.80   $1,050.80