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	$232.91	11.633%	$260.0044	$260.00	$260.00	$260.00
Purchase #2	$107.42	6.720%	$114.6386	$114.64	$114.65	$114.60
Purchase #3	$35.49	5.605%	$37.4792	$37.48	$37.50	$37.50
Purchase #4	$144.39	11.425%	$160.8866	$160.89	$160.90	$160.90
Purchase #5	$232.86	9.404%	$254.7582	$254.76	$254.75	$254.80
Purchase #6	$152.35	13.824%	$173.4109	$173.41	$173.40	$173.40
Purchase #7	$182.46	4.520%	$190.7072	$190.71	$190.70	$190.70
7 purchase totals =	$1,087.88		$1,191.8851	$1,191.89	$1,191.90	$1,191.90