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	$114.31	11.301%	$127.2282	$127.23	$127.25	$127.20
Purchase #2	$98.70	12.551%	$111.0878	$111.09	$111.10	$111.10
Purchase #3	$27.65	7.105%	$29.6145	$29.61	$29.60	$29.60
Purchase #4	$55.76	6.610%	$59.4457	$59.45	$59.45	$59.40
Purchase #5	$202.41	10.466%	$223.5942	$223.59	$223.60	$223.60
Purchase #6	$99.41	5.427%	$104.805	$104.81	$104.80	$104.80
Purchase #7	$228.84	10.835%	$253.6348	$253.63	$253.65	$253.60
7 purchase totals =	$827.08		$909.4102	$909.41	$909.45	$909.30