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	$224.30	10.362%	$247.542	$247.54	$247.55	$247.50
Purchase #2	$127.60	8.162%	$138.0147	$138.01	$138.00	$138.00
Purchase #3	$189.74	8.705%	$206.2569	$206.26	$206.25	$206.30
Purchase #4	$145.77	8.758%	$158.5365	$158.54	$158.55	$158.50
Purchase #5	$87.70	8.211%	$94.901	$94.90	$94.90	$94.90
Purchase #6	$96.53	4.154%	$100.5399	$100.54	$100.55	$100.50
Purchase #7	$158.55	6.500%	$168.8558	$168.86	$168.85	$168.90
7 purchase totals =	$1,030.19		$1,114.6468	$1,114.65	$1,114.65	$1,114.60