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	$177.62	6.527%	$189.2133	$189.21	$189.20	$189.20
Purchase #2	$129.27	3.318%	$133.5592	$133.56	$133.55	$133.60
Purchase #3	$134.49	5.770%	$142.2501	$142.25	$142.25	$142.30
Purchase #4	$168.46	7.459%	$181.0254	$181.03	$181.05	$181.00
Purchase #5	$86.73	5.661%	$91.6398	$91.64	$91.65	$91.60
Purchase #6	$49.67	7.733%	$53.511	$53.51	$53.50	$53.50
Purchase #7	$213.65	5.555%	$225.5183	$225.52	$225.50	$225.50
7 purchase totals =	$959.89		$1,016.7171	$1,016.72	$1,016.70	$1,016.70