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	$199.37	8.160%	$215.6386	$215.64	$215.65	$215.60
Purchase #2	$91.92	13.566%	$104.3899	$104.39	$104.40	$104.40
Purchase #3	$109.90	12.172%	$123.277	$123.28	$123.30	$123.30
Purchase #4	$193.33	6.857%	$206.5866	$206.59	$206.60	$206.60
Purchase #5	$98.75	3.222%	$101.9317	$101.93	$101.95	$101.90
Purchase #6	$79.52	8.195%	$86.0367	$86.04	$86.05	$86.00
Purchase #7	$73.43	7.503%	$78.9395	$78.94	$78.95	$78.90
7 purchase totals =	$846.22		$916.8000	$916.81	$916.90	$916.70