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	$42.63	5.194%	$44.8442	$44.84	$44.85	$44.80
Purchase #2	$185.79	9.302%	$203.0722	$203.07	$203.05	$203.10
Purchase #3	$72.60	8.197%	$78.551	$78.55	$78.55	$78.60
Purchase #4	$115.60	8.363%	$125.2676	$125.27	$125.25	$125.30
Purchase #5	$50.84	11.145%	$56.5061	$56.51	$56.50	$56.50
Purchase #6	$181.54	8.141%	$196.3192	$196.32	$196.30	$196.30
Purchase #7	$12.72	10.734%	$14.0854	$14.09	$14.10	$14.10
7 purchase totals =	$661.72		$718.6457	$718.65	$718.60	$718.70