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	$238.90	12.722%	$269.2929	$269.29	$269.30	$269.30
Purchase #2	$199.70	8.193%	$216.0614	$216.06	$216.05	$216.10
Purchase #3	$50.70	11.622%	$56.5924	$56.59	$56.60	$56.60
Purchase #4	$19.76	3.152%	$20.3828	$20.38	$20.40	$20.40
Purchase #5	$35.39	11.498%	$39.4591	$39.46	$39.45	$39.50
Purchase #6	$125.91	13.858%	$143.3586	$143.36	$143.35	$143.40
Purchase #7	$70.87	12.770%	$79.9201	$79.92	$79.90	$79.90
7 purchase totals =	$741.23		$825.0673	$825.06	$825.05	$825.20