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	$230.37	4.768%	$241.354	$241.35	$241.35	$241.40
Purchase #2	$173.82	5.779%	$183.8651	$183.87	$183.85	$183.90
Purchase #3	$116.49	9.503%	$127.56	$127.56	$127.55	$127.60
Purchase #4	$153.54	11.110%	$170.5983	$170.60	$170.60	$170.60
Purchase #5	$19.46	12.255%	$21.8448	$21.84	$21.85	$21.80
Purchase #6	$40.29	12.750%	$45.427	$45.43	$45.45	$45.40
Purchase #7	$123.44	4.201%	$128.6257	$128.63	$128.65	$128.60
7 purchase totals =	$857.41		$919.2749	$919.28	$919.30	$919.30