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	$228.33	3.121%	$235.4562	$235.46	$235.45	$235.50
Purchase #2	$214.74	7.605%	$231.071	$231.07	$231.05	$231.10
Purchase #3	$168.87	5.493%	$178.146	$178.15	$178.15	$178.10
Purchase #4	$24.39	13.398%	$27.6578	$27.66	$27.65	$27.70
Purchase #5	$61.85	9.340%	$67.6268	$67.63	$67.65	$67.60
Purchase #6	$87.92	4.557%	$91.9265	$91.93	$91.95	$91.90
Purchase #7	$236.27	5.846%	$250.0823	$250.08	$250.10	$250.10
7 purchase totals =	$1,022.37		$1,081.9666	$1,081.98	$1,082.00	$1,082.00