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 $241.28   8.673%   $262.2062   $262.21   $262.20   $262.20  
  Purchase #2 $153.96   10.294%   $169.8086   $169.81   $169.80   $169.80  
  Purchase #3 $20.51   9.806%   $22.5212   $22.52   $22.50   $22.50  
  Purchase #4 $117.64   7.167%   $126.0713   $126.07   $126.05   $126.10  
  Purchase #5 $135.98   13.505%   $154.3441   $154.34   $154.35   $154.30  
  Purchase #6 $122.74   3.274%   $126.7585   $126.76   $126.75   $126.80  
  Purchase #7 $234.42   3.413%   $242.4208   $242.42   $242.40   $242.40  
  7 purchase totals = $1,026.53       $1,104.1307   $1,104.13   $1,104.05   $1,104.10