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	$105.74	5.353%	$111.4003	$111.40	$111.40	$111.40
Purchase #2	$223.49	9.836%	$245.4725	$245.47	$245.45	$245.50
Purchase #3	$68.52	13.647%	$77.8709	$77.87	$77.85	$77.90
Purchase #4	$131.27	6.267%	$139.4967	$139.50	$139.50	$139.50
Purchase #5	$202.29	6.419%	$215.275	$215.28	$215.30	$215.30
Purchase #6	$95.69	12.734%	$107.8752	$107.88	$107.90	$107.90
Purchase #7	$136.69	13.413%	$155.0242	$155.02	$155.00	$155.00
7 purchase totals =	$963.69		$1,052.4148	$1,052.42	$1,052.40	$1,052.50