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	$36.39	3.819%	$37.7797	$37.78	$37.80	$37.80
Purchase #2	$240.95	5.456%	$254.0962	$254.10	$254.10	$254.10
Purchase #3	$201.39	13.602%	$228.7831	$228.78	$228.80	$228.80
Purchase #4	$93.48	7.275%	$100.2807	$100.28	$100.30	$100.30
Purchase #5	$47.64	8.827%	$51.8452	$51.85	$51.85	$51.80
Purchase #6	$166.35	7.575%	$178.951	$178.95	$178.95	$179.00
Purchase #7	$151.48	7.295%	$162.5305	$162.53	$162.55	$162.50
7 purchase totals =	$937.68		$1,014.2664	$1,014.27	$1,014.35	$1,014.30