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	$238.27	5.738%	$251.9419	$251.94	$251.95	$251.90
Purchase #2	$223.39	8.454%	$242.2754	$242.28	$242.30	$242.30
Purchase #3	$175.93	11.129%	$195.5092	$195.51	$195.50	$195.50
Purchase #4	$29.52	9.472%	$32.3161	$32.32	$32.30	$32.30
Purchase #5	$45.76	13.301%	$51.8465	$51.85	$51.85	$51.80
Purchase #6	$248.74	13.233%	$281.6558	$281.66	$281.65	$281.70
Purchase #7	$116.48	6.240%	$123.7484	$123.75	$123.75	$123.70
7 purchase totals =	$1,078.09		$1,179.2933	$1,179.31	$1,179.30	$1,179.20