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	$56.46	5.694%	$59.6748	$59.67	$59.65	$59.70
Purchase #2	$102.84	9.358%	$112.4638	$112.46	$112.45	$112.50
Purchase #3	$215.25	12.856%	$242.9225	$242.92	$242.90	$242.90
Purchase #4	$205.78	8.104%	$222.4564	$222.46	$222.45	$222.50
Purchase #5	$180.95	5.157%	$190.2816	$190.28	$190.30	$190.30
Purchase #6	$98.80	11.204%	$109.8696	$109.87	$109.85	$109.90
Purchase #7	$127.41	7.826%	$137.3811	$137.38	$137.40	$137.40
7 purchase totals =	$987.49		$1,075.0498	$1,075.04	$1,075.00	$1,075.20