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	$245.76	10.508%	$271.5845	$271.58	$271.60	$271.60
Purchase #2	$11.54	7.553%	$12.4116	$12.41	$12.40	$12.40
Purchase #3	$138.74	9.613%	$152.0771	$152.08	$152.10	$152.10
Purchase #4	$134.59	8.349%	$145.8269	$145.83	$145.85	$145.80
Purchase #5	$119.36	3.532%	$123.5758	$123.58	$123.60	$123.60
Purchase #6	$181.55	13.243%	$205.5927	$205.59	$205.60	$205.60
Purchase #7	$109.62	4.800%	$114.8818	$114.88	$114.90	$114.90
7 purchase totals =	$941.16		$1,025.9504	$1,025.95	$1,026.05	$1,026.00