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	$54.44	13.805%	$61.9554	$61.96	$61.95	$62.00
Purchase #2	$152.55	12.383%	$171.4403	$171.44	$171.45	$171.40
Purchase #3	$48.54	7.359%	$52.1121	$52.11	$52.10	$52.10
Purchase #4	$127.36	4.215%	$132.7282	$132.73	$132.75	$132.70
Purchase #5	$20.77	12.723%	$23.4126	$23.41	$23.40	$23.40
Purchase #6	$11.42	11.404%	$12.7223	$12.72	$12.70	$12.70
Purchase #7	$98.83	6.388%	$105.1433	$105.14	$105.15	$105.10
7 purchase totals =	$513.91		$559.5142	$559.51	$559.50	$559.40