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	$205.63	9.388%	$224.9345	$224.93	$224.95	$224.90
Purchase #2	$133.97	4.128%	$139.5003	$139.50	$139.50	$139.50
Purchase #3	$30.32	11.287%	$33.7422	$33.74	$33.75	$33.70
Purchase #4	$70.71	10.367%	$78.0405	$78.04	$78.05	$78.00
Purchase #5	$182.66	4.288%	$190.4925	$190.49	$190.50	$190.50
Purchase #6	$171.63	11.667%	$191.6541	$191.65	$191.65	$191.70
Purchase #7	$97.77	13.437%	$110.9074	$110.91	$110.90	$110.90
7 purchase totals =	$892.69		$969.2715	$969.26	$969.30	$969.20