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	$59.33	13.664%	$67.4369	$67.44	$67.45	$67.40
Purchase #2	$39.47	6.587%	$42.0699	$42.07	$42.05	$42.10
Purchase #3	$233.64	11.592%	$260.7235	$260.72	$260.70	$260.70
Purchase #4	$79.42	13.848%	$90.4181	$90.42	$90.40	$90.40
Purchase #5	$60.87	3.463%	$62.9779	$62.98	$63.00	$63.00
Purchase #6	$101.33	6.313%	$107.727	$107.73	$107.75	$107.70
Purchase #7	$60.42	3.365%	$62.4531	$62.45	$62.45	$62.50
7 purchase totals =	$634.48		$693.8064	$693.81	$693.80	$693.80