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	$58.65	12.196%	$65.803	$65.80	$65.80	$65.80
Purchase #2	$194.80	11.191%	$216.6001	$216.60	$216.60	$216.60
Purchase #3	$122.97	9.716%	$134.9178	$134.92	$134.90	$134.90
Purchase #4	$91.85	10.314%	$101.3234	$101.32	$101.30	$101.30
Purchase #5	$90.66	11.332%	$100.9336	$100.93	$100.95	$100.90
Purchase #6	$235.90	6.498%	$251.2288	$251.23	$251.25	$251.20
Purchase #7	$173.95	6.148%	$184.6444	$184.64	$184.65	$184.60
7 purchase totals =	$968.78		$1,055.4511	$1,055.44	$1,055.45	$1,055.30