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	$225.90	11.287%	$251.3973	$251.40	$251.40	$251.40
Purchase #2	$216.57	11.487%	$241.4474	$241.45	$241.45	$241.40
Purchase #3	$57.50	3.142%	$59.3067	$59.31	$59.30	$59.30
Purchase #4	$220.76	11.320%	$245.75	$245.75	$245.75	$245.80
Purchase #5	$8.48	4.548%	$8.8657	$8.87	$8.85	$8.90
Purchase #6	$135.54	7.540%	$145.7597	$145.76	$145.75	$145.80
Purchase #7	$127.32	5.842%	$134.758	$134.76	$134.75	$134.80
7 purchase totals =	$992.07		$1,087.2848	$1,087.30	$1,087.25	$1,087.40