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 $205.27   4.504%   $214.5154   $214.52   $214.50   $214.50  
  Purchase #2 $61.60   6.523%   $65.6182   $65.62   $65.60   $65.60  
  Purchase #3 $143.28   7.573%   $154.1306   $154.13   $154.15   $154.10  
  Purchase #4 $209.94   3.514%   $217.3173   $217.32   $217.30   $217.30  
  Purchase #5 $151.34   12.153%   $169.7324   $169.73   $169.75   $169.70  
  Purchase #6 $163.39   12.748%   $184.219   $184.22   $184.20   $184.20  
  Purchase #7 $35.70   8.852%   $38.8602   $38.86   $38.85   $38.90  
  7 purchase totals = $970.52       $1,044.3931   $1,044.40   $1,044.35   $1,044.30