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	$186.73	5.346%	$196.7126	$196.71	$196.70	$196.70
Purchase #2	$7.85	5.298%	$8.2659	$8.27	$8.25	$8.30
Purchase #3	$179.42	3.533%	$185.7589	$185.76	$185.75	$185.80
Purchase #4	$177.50	10.472%	$196.0878	$196.09	$196.10	$196.10
Purchase #5	$33.39	3.831%	$34.6692	$34.67	$34.65	$34.70
Purchase #6	$100.38	6.456%	$106.8605	$106.86	$106.85	$106.90
Purchase #7	$100.83	3.269%	$104.1261	$104.13	$104.15	$104.10
7 purchase totals =	$786.10		$832.4810	$832.49	$832.45	$832.60