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	$162.78	4.291%	$169.7649	$169.76	$169.75	$169.80
Purchase #2	$12.37	11.483%	$13.7904	$13.79	$13.80	$13.80
Purchase #3	$101.45	4.236%	$105.7474	$105.75	$105.75	$105.70
Purchase #4	$175.37	8.642%	$190.5255	$190.53	$190.55	$190.50
Purchase #5	$38.83	8.104%	$41.9768	$41.98	$42.00	$42.00
Purchase #6	$101.76	10.699%	$112.6473	$112.65	$112.65	$112.60
Purchase #7	$249.95	8.570%	$271.3707	$271.37	$271.35	$271.40
7 purchase totals =	$842.51		$905.8230	$905.83	$905.85	$905.80