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	$56.56	11.142%	$62.8619	$62.86	$62.85	$62.90
Purchase #2	$149.46	6.218%	$158.7534	$158.75	$158.75	$158.80
Purchase #3	$224.70	6.601%	$239.5324	$239.53	$239.55	$239.50
Purchase #4	$42.38	3.629%	$43.918	$43.92	$43.90	$43.90
Purchase #5	$187.65	6.304%	$199.4795	$199.48	$199.50	$199.50
Purchase #6	$27.61	6.592%	$29.4301	$29.43	$29.45	$29.40
Purchase #7	$48.33	13.206%	$54.7125	$54.71	$54.70	$54.70
7 purchase totals =	$736.69		$788.6878	$788.68	$788.70	$788.70