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 $58.33   6.534%   $62.1413   $62.14   $62.15   $62.10  
  Purchase #2 $60.69   10.313%   $66.949   $66.95   $66.95   $66.90  
  Purchase #3 $85.29   7.788%   $91.9324   $91.93   $91.95   $91.90  
  Purchase #4 $228.68   8.409%   $247.9097   $247.91   $247.90   $247.90  
  Purchase #5 $215.71   8.317%   $233.6506   $233.65   $233.65   $233.70  
  Purchase #6 $243.80   5.341%   $256.8214   $256.82   $256.80   $256.80  
  Purchase #7 $106.83   3.304%   $110.3597   $110.36   $110.35   $110.40  
  7 purchase totals = $999.33       $1,069.7641   $1,069.76   $1,069.75   $1,069.70