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	$201.94	11.422%	$225.0056	$225.01	$225.00	$225.00
Purchase #2	$88.67	13.348%	$100.5057	$100.51	$100.50	$100.50
Purchase #3	$10.35	11.109%	$11.4998	$11.50	$11.50	$11.50
Purchase #4	$115.27	10.234%	$127.0667	$127.07	$127.05	$127.10
Purchase #5	$174.95	5.694%	$184.9117	$184.91	$184.90	$184.90
Purchase #6	$220.46	9.208%	$240.76	$240.76	$240.75	$240.80
Purchase #7	$210.92	9.530%	$231.0207	$231.02	$231.00	$231.00
7 purchase totals =	$1,022.56		$1,120.7702	$1,120.78	$1,120.70	$1,120.80