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	$112.42	5.726%	$118.8572	$118.86	$118.85	$118.90
Purchase #2	$162.69	10.471%	$179.7253	$179.73	$179.75	$179.70
Purchase #3	$77.81	6.573%	$82.9245	$82.92	$82.90	$82.90
Purchase #4	$26.78	10.258%	$29.5271	$29.53	$29.55	$29.50
Purchase #5	$207.41	3.248%	$214.1467	$214.15	$214.15	$214.10
Purchase #6	$131.47	7.279%	$141.0397	$141.04	$141.05	$141.00
Purchase #7	$187.54	6.265%	$199.2894	$199.29	$199.30	$199.30
7 purchase totals =	$906.12		$965.5099	$965.52	$965.55	$965.40