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	$223.32	8.119%	$241.4514	$241.45	$241.45	$241.50
Purchase #2	$43.62	9.548%	$47.7848	$47.78	$47.80	$47.80
Purchase #3	$27.66	11.680%	$30.8907	$30.89	$30.90	$30.90
Purchase #4	$70.70	11.391%	$78.7534	$78.75	$78.75	$78.80
Purchase #5	$41.44	5.851%	$43.8647	$43.86	$43.85	$43.90
Purchase #6	$123.77	7.561%	$133.1282	$133.13	$133.15	$133.10
Purchase #7	$44.59	4.666%	$46.6706	$46.67	$46.65	$46.70
7 purchase totals =	$575.10		$622.5438	$622.53	$622.55	$622.70