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	$84.69	11.718%	$94.614	$94.61	$94.60	$94.60
Purchase #2	$233.31	6.749%	$249.0561	$249.06	$249.05	$249.10
Purchase #3	$217.39	8.620%	$236.129	$236.13	$236.15	$236.10
Purchase #4	$141.35	11.860%	$158.1141	$158.11	$158.10	$158.10
Purchase #5	$200.28	4.137%	$208.5656	$208.57	$208.55	$208.60
Purchase #6	$85.27	12.719%	$96.1155	$96.12	$96.10	$96.10
Purchase #7	$92.85	8.404%	$100.6531	$100.65	$100.65	$100.70
7 purchase totals =	$1,055.14		$1,143.2474	$1,143.25	$1,143.20	$1,143.30