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	$52.73	6.472%	$56.1427	$56.14	$56.15	$56.10
Purchase #2	$140.49	7.861%	$151.5339	$151.53	$151.55	$151.50
Purchase #3	$105.95	3.569%	$109.7314	$109.73	$109.75	$109.70
Purchase #4	$242.74	11.140%	$269.7812	$269.78	$269.80	$269.80
Purchase #5	$11.64	11.768%	$13.0098	$13.01	$13.00	$13.00
Purchase #6	$53.56	5.112%	$56.298	$56.30	$56.30	$56.30
Purchase #7	$44.80	4.517%	$46.8236	$46.82	$46.80	$46.80
7 purchase totals =	$651.91		$703.3206	$703.31	$703.35	$703.20