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 $182.46   8.790%   $198.4982   $198.50   $198.50   $198.50  
  Purchase #2 $166.25   10.799%   $184.2033   $184.20   $184.20   $184.20  
  Purchase #3 $201.38   9.644%   $220.8011   $220.80   $220.80   $220.80  
  Purchase #4 $96.90   8.272%   $104.9156   $104.92   $104.90   $104.90  
  Purchase #5 $100.94   5.152%   $106.1404   $106.14   $106.15   $106.10  
  Purchase #6 $40.51   6.869%   $43.2926   $43.29   $43.30   $43.30  
  Purchase #7 $142.63   8.333%   $154.5154   $154.52   $154.50   $154.50  
  7 purchase totals = $931.07       $1,012.3666   $1,012.37   $1,012.35   $1,012.30