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	$111.50	7.247%	$119.5804	$119.58	$119.60	$119.60
Purchase #2	$239.57	13.224%	$271.2507	$271.25	$271.25	$271.30
Purchase #3	$86.53	4.205%	$90.1686	$90.17	$90.15	$90.20
Purchase #4	$215.75	7.613%	$232.175	$232.18	$232.20	$232.20
Purchase #5	$230.76	3.302%	$238.3797	$238.38	$238.40	$238.40
Purchase #6	$119.87	9.638%	$131.4231	$131.42	$131.40	$131.40
Purchase #7	$118.56	7.133%	$127.0169	$127.02	$127.00	$127.00
7 purchase totals =	$1,122.54		$1,209.9944	$1,210.00	$1,210.00	$1,210.10