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	$236.30	4.142%	$246.0875	$246.09	$246.10	$246.10
Purchase #2	$59.55	7.232%	$63.8567	$63.86	$63.85	$63.90
Purchase #3	$155.71	7.199%	$166.9196	$166.92	$166.90	$166.90
Purchase #4	$52.45	4.224%	$54.6655	$54.67	$54.65	$54.70
Purchase #5	$103.80	9.514%	$113.6755	$113.68	$113.70	$113.70
Purchase #6	$176.96	13.181%	$200.2851	$200.29	$200.30	$200.30
Purchase #7	$77.97	6.276%	$82.8634	$82.86	$82.85	$82.90
7 purchase totals =	$862.74		$928.3533	$928.37	$928.35	$928.50