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 $226.46   6.561%   $241.318   $241.32   $241.30   $241.30  
  Purchase #2 $119.59   3.868%   $124.2157   $124.22   $124.20   $124.20  
  Purchase #3 $175.31   5.863%   $185.5884   $185.59   $185.60   $185.60  
  Purchase #4 $100.62   12.515%   $113.2126   $113.21   $113.20   $113.20  
  Purchase #5 $166.90   6.365%   $177.5232   $177.52   $177.50   $177.50  
  Purchase #6 $158.90   7.592%   $170.9637   $170.96   $170.95   $171.00  
  Purchase #7 $153.43   5.494%   $161.8594   $161.86   $161.85   $161.90  
  7 purchase totals = $1,101.21       $1,174.6810   $1,174.68   $1,174.60   $1,174.70