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	$43.47	5.471%	$45.8482	$45.85	$45.85	$45.80
Purchase #2	$226.92	3.840%	$235.6337	$235.63	$235.65	$235.60
Purchase #3	$40.29	13.706%	$45.8121	$45.81	$45.80	$45.80
Purchase #4	$158.69	3.410%	$164.1013	$164.10	$164.10	$164.10
Purchase #5	$18.64	9.598%	$20.4291	$20.43	$20.45	$20.40
Purchase #6	$152.42	6.324%	$162.059	$162.06	$162.05	$162.10
Purchase #7	$37.53	7.411%	$40.3113	$40.31	$40.30	$40.30
7 purchase totals =	$677.96		$714.1947	$714.19	$714.20	$714.10