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	$205.66	11.509%	$229.3294	$229.33	$229.35	$229.30
Purchase #2	$19.91	12.215%	$22.342	$22.34	$22.35	$22.30
Purchase #3	$121.33	11.108%	$134.8073	$134.81	$134.80	$134.80
Purchase #4	$244.56	6.647%	$260.8159	$260.82	$260.80	$260.80
Purchase #5	$158.51	11.441%	$176.6451	$176.65	$176.65	$176.60
Purchase #6	$37.73	12.688%	$42.5172	$42.52	$42.50	$42.50
Purchase #7	$217.30	10.130%	$239.3125	$239.31	$239.30	$239.30
7 purchase totals =	$1,005.00		$1,105.7694	$1,105.78	$1,105.75	$1,105.60