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	$102.73	11.579%	$114.6251	$114.63	$114.65	$114.60
Purchase #2	$122.82	6.159%	$130.3845	$130.38	$130.40	$130.40
Purchase #3	$127.65	6.650%	$136.1387	$136.14	$136.15	$136.10
Purchase #4	$129.93	9.512%	$142.2889	$142.29	$142.30	$142.30
Purchase #5	$47.85	5.333%	$50.4018	$50.40	$50.40	$50.40
Purchase #6	$101.32	4.341%	$105.7183	$105.72	$105.70	$105.70
Purchase #7	$89.96	5.582%	$94.9816	$94.98	$95.00	$95.00
7 purchase totals =	$722.26		$774.5389	$774.54	$774.60	$774.50