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	$215.60	3.746%	$223.6764	$223.68	$223.70	$223.70
Purchase #2	$204.50	11.841%	$228.7148	$228.71	$228.70	$228.70
Purchase #3	$131.64	8.283%	$142.5437	$142.54	$142.55	$142.50
Purchase #4	$45.28	6.338%	$48.1498	$48.15	$48.15	$48.10
Purchase #5	$156.25	5.245%	$164.4453	$164.45	$164.45	$164.40
Purchase #6	$54.99	11.733%	$61.442	$61.44	$61.45	$61.40
Purchase #7	$214.96	11.816%	$240.3597	$240.36	$240.35	$240.40
7 purchase totals =	$1,023.22		$1,109.3317	$1,109.33	$1,109.35	$1,109.20