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	$49.73	11.846%	$55.621	$55.62	$55.60	$55.60
Purchase #2	$18.32	7.360%	$19.6684	$19.67	$19.65	$19.70
Purchase #3	$55.29	7.104%	$59.2178	$59.22	$59.20	$59.20
Purchase #4	$136.29	6.124%	$144.6364	$144.64	$144.65	$144.60
Purchase #5	$127.73	12.707%	$143.9607	$143.96	$143.95	$144.00
Purchase #6	$60.75	11.545%	$67.7636	$67.76	$67.75	$67.80
Purchase #7	$237.76	6.845%	$254.0347	$254.03	$254.05	$254.00
7 purchase totals =	$685.87		$744.9026	$744.90	$744.85	$744.90