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 $219.47   6.598%   $233.9506   $233.95   $233.95   $234.00  
  Purchase #2 $198.95   9.423%   $217.6971   $217.70   $217.70   $217.70  
  Purchase #3 $95.61   4.619%   $100.0262   $100.03   $100.05   $100.00  
  Purchase #4 $137.30   7.763%   $147.9586   $147.96   $147.95   $148.00  
  Purchase #5 $229.97   10.770%   $254.7378   $254.74   $254.75   $254.70  
  Purchase #6 $218.46   11.736%   $244.0985   $244.10   $244.10   $244.10  
  Purchase #7 $159.47   5.271%   $167.8757   $167.88   $167.90   $167.90  
  7 purchase totals = $1,259.23       $1,366.3445   $1,366.36   $1,366.40   $1,366.40