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	$224.93	13.216%	$254.6567	$254.66	$254.65	$254.70
Purchase #2	$218.41	3.163%	$225.3183	$225.32	$225.30	$225.30
Purchase #3	$231.90	13.211%	$262.5363	$262.54	$262.55	$262.50
Purchase #4	$43.30	6.422%	$46.0807	$46.08	$46.10	$46.10
Purchase #5	$31.83	4.858%	$33.3763	$33.38	$33.40	$33.40
Purchase #6	$187.99	5.825%	$198.9404	$198.94	$198.95	$198.90
Purchase #7	$154.71	13.428%	$175.4845	$175.48	$175.50	$175.50
7 purchase totals =	$1,093.07		$1,196.3932	$1,196.40	$1,196.45	$1,196.40