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	$43.66	4.317%	$45.5448	$45.54	$45.55	$45.50
Purchase #2	$117.43	13.694%	$133.5109	$133.51	$133.50	$133.50
Purchase #3	$247.88	6.261%	$263.3998	$263.40	$263.40	$263.40
Purchase #4	$185.97	5.793%	$196.7432	$196.74	$196.75	$196.70
Purchase #5	$187.32	8.581%	$203.3939	$203.39	$203.40	$203.40
Purchase #6	$167.65	10.248%	$184.8308	$184.83	$184.85	$184.80
Purchase #7	$187.86	6.564%	$200.1911	$200.19	$200.20	$200.20
7 purchase totals =	$1,137.77		$1,227.6145	$1,227.60	$1,227.65	$1,227.50