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	$94.84	13.657%	$107.7923	$107.79	$107.80	$107.80
Purchase #2	$151.36	7.215%	$162.2806	$162.28	$162.30	$162.30
Purchase #3	$199.99	11.352%	$222.6929	$222.69	$222.70	$222.70
Purchase #4	$63.46	11.686%	$70.8759	$70.88	$70.90	$70.90
Purchase #5	$108.27	13.241%	$122.606	$122.61	$122.60	$122.60
Purchase #6	$92.76	11.741%	$103.651	$103.65	$103.65	$103.70
Purchase #7	$100.32	11.142%	$111.4977	$111.50	$111.50	$111.50
7 purchase totals =	$811.00		$901.3964	$901.40	$901.45	$901.50