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	$75.66	8.464%	$82.0639	$82.06	$82.05	$82.10
Purchase #2	$43.52	4.858%	$45.6342	$45.63	$45.65	$45.60
Purchase #3	$243.78	6.543%	$259.7305	$259.73	$259.75	$259.70
Purchase #4	$36.83	10.275%	$40.6143	$40.61	$40.60	$40.60
Purchase #5	$126.38	11.182%	$140.5118	$140.51	$140.50	$140.50
Purchase #6	$161.69	6.127%	$171.5967	$171.60	$171.60	$171.60
Purchase #7	$10.95	3.680%	$11.353	$11.35	$11.35	$11.40
7 purchase totals =	$698.81		$751.5044	$751.49	$751.50	$751.50