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	$207.52	4.272%	$216.3853	$216.39	$216.40	$216.40
Purchase #2	$46.53	6.549%	$49.5772	$49.58	$49.60	$49.60
Purchase #3	$136.85	5.270%	$144.062	$144.06	$144.05	$144.10
Purchase #4	$92.51	8.393%	$100.2744	$100.27	$100.25	$100.30
Purchase #5	$56.71	3.787%	$58.8576	$58.86	$58.85	$58.90
Purchase #6	$189.86	3.241%	$196.0134	$196.01	$196.00	$196.00
Purchase #7	$114.88	6.313%	$122.1324	$122.13	$122.15	$122.10
7 purchase totals =	$844.86		$887.3023	$887.30	$887.30	$887.40