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	$40.63	11.177%	$45.1712	$45.17	$45.15	$45.20
Purchase #2	$148.43	5.145%	$156.0667	$156.07	$156.05	$156.10
Purchase #3	$72.71	13.235%	$82.3332	$82.33	$82.35	$82.30
Purchase #4	$153.39	4.234%	$159.8845	$159.88	$159.90	$159.90
Purchase #5	$94.54	13.650%	$107.4447	$107.44	$107.45	$107.40
Purchase #6	$46.84	13.231%	$53.0374	$53.04	$53.05	$53.00
Purchase #7	$231.58	12.438%	$260.3839	$260.38	$260.40	$260.40
7 purchase totals =	$788.12		$864.3216	$864.31	$864.35	$864.30