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	$112.69	3.180%	$116.2735	$116.27	$116.25	$116.30
Purchase #2	$99.95	11.474%	$111.4183	$111.42	$111.40	$111.40
Purchase #3	$51.87	6.214%	$55.0932	$55.09	$55.10	$55.10
Purchase #4	$124.47	6.706%	$132.817	$132.82	$132.80	$132.80
Purchase #5	$180.64	10.203%	$199.0707	$199.07	$199.05	$199.10
Purchase #6	$183.72	4.734%	$192.4173	$192.42	$192.40	$192.40
Purchase #7	$84.29	8.292%	$91.2793	$91.28	$91.30	$91.30
7 purchase totals =	$837.63		$898.3693	$898.37	$898.30	$898.40