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	$92.88	6.272%	$98.7054	$98.71	$98.70	$98.70
Purchase #2	$12.68	6.664%	$13.525	$13.53	$13.55	$13.50
Purchase #3	$41.32	4.684%	$43.2554	$43.26	$43.25	$43.30
Purchase #4	$88.45	13.730%	$100.5942	$100.59	$100.60	$100.60
Purchase #5	$113.25	7.635%	$121.8966	$121.90	$121.90	$121.90
Purchase #6	$40.52	5.457%	$42.7312	$42.73	$42.75	$42.70
Purchase #7	$99.50	12.305%	$111.7435	$111.74	$111.75	$111.70
7 purchase totals =	$488.60		$532.4513	$532.46	$532.50	$532.40