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	$113.52	9.114%	$123.8662	$123.87	$123.85	$123.90
Purchase #2	$172.74	4.280%	$180.1333	$180.13	$180.15	$180.10
Purchase #3	$162.30	9.845%	$178.2784	$178.28	$178.30	$178.30
Purchase #4	$114.71	11.210%	$127.569	$127.57	$127.55	$127.60
Purchase #5	$149.84	8.581%	$162.6978	$162.70	$162.70	$162.70
Purchase #6	$144.30	11.102%	$160.3202	$160.32	$160.30	$160.30
Purchase #7	$46.59	8.691%	$50.6391	$50.64	$50.65	$50.60
7 purchase totals =	$904.00		$983.5040	$983.51	$983.50	$983.50