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 $244.81   7.103%   $262.1989   $262.20   $262.20   $262.20  
  Purchase #2 $44.61   6.147%   $47.3522   $47.35   $47.35   $47.40  
  Purchase #3 $212.74   7.598%   $228.904   $228.90   $228.90   $228.90  
  Purchase #4 $203.35   4.710%   $212.9278   $212.93   $212.95   $212.90  
  Purchase #5 $161.28   5.564%   $170.2536   $170.25   $170.25   $170.30  
  Purchase #6 $126.36   6.718%   $134.8489   $134.85   $134.85   $134.80  
  Purchase #7 $65.87   8.544%   $71.4979   $71.50   $71.50   $71.50  
  7 purchase totals = $1,059.02       $1,127.9833   $1,127.98   $1,128.00   $1,128.00