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	$62.81	12.826%	$70.866	$70.87	$70.85	$70.90
Purchase #2	$182.70	8.397%	$198.0413	$198.04	$198.05	$198.00
Purchase #3	$71.55	6.803%	$76.4175	$76.42	$76.40	$76.40
Purchase #4	$39.43	3.123%	$40.6614	$40.66	$40.65	$40.70
Purchase #5	$102.70	3.610%	$106.4075	$106.41	$106.40	$106.40
Purchase #6	$86.32	4.349%	$90.0741	$90.07	$90.05	$90.10
Purchase #7	$183.26	3.705%	$190.0498	$190.05	$190.05	$190.00
7 purchase totals =	$728.77		$772.5176	$772.52	$772.45	$772.50