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	$106.66	4.835%	$111.817	$111.82	$111.80	$111.80
Purchase #2	$247.61	3.777%	$256.9622	$256.96	$256.95	$257.00
Purchase #3	$219.78	7.716%	$236.7382	$236.74	$236.75	$236.70
Purchase #4	$128.83	8.388%	$139.6363	$139.64	$139.65	$139.60
Purchase #5	$167.82	8.476%	$182.0444	$182.04	$182.05	$182.00
Purchase #6	$199.70	11.798%	$223.2606	$223.26	$223.25	$223.30
Purchase #7	$229.70	13.222%	$260.0709	$260.07	$260.05	$260.10
7 purchase totals =	$1,300.10		$1,410.5296	$1,410.53	$1,410.50	$1,410.50