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	$102.64	9.244%	$112.128	$112.13	$112.15	$112.10
Purchase #2	$35.94	3.598%	$37.2331	$37.23	$37.25	$37.20
Purchase #3	$121.78	5.487%	$128.4621	$128.46	$128.45	$128.50
Purchase #4	$122.89	6.845%	$131.3018	$131.30	$131.30	$131.30
Purchase #5	$110.48	9.572%	$121.0551	$121.06	$121.05	$121.10
Purchase #6	$100.56	8.114%	$108.7194	$108.72	$108.70	$108.70
Purchase #7	$225.61	4.455%	$235.6609	$235.66	$235.65	$235.70
7 purchase totals =	$819.90		$874.5604	$874.56	$874.55	$874.60