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	$151.30	4.629%	$158.3037	$158.30	$158.30	$158.30
Purchase #2	$48.41	12.836%	$54.6239	$54.62	$54.60	$54.60
Purchase #3	$210.77	11.398%	$234.7936	$234.79	$234.80	$234.80
Purchase #4	$154.73	3.579%	$160.2678	$160.27	$160.25	$160.30
Purchase #5	$137.92	5.538%	$145.558	$145.56	$145.55	$145.60
Purchase #6	$89.63	12.190%	$100.5559	$100.56	$100.55	$100.60
Purchase #7	$28.86	9.823%	$31.6949	$31.69	$31.70	$31.70
7 purchase totals =	$821.62		$885.7978	$885.79	$885.75	$885.90