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	$58.82	11.407%	$65.5296	$65.53	$65.55	$65.50
Purchase #2	$236.76	6.249%	$251.5551	$251.56	$251.55	$251.60
Purchase #3	$122.60	5.181%	$128.9519	$128.95	$128.95	$129.00
Purchase #4	$82.86	4.542%	$86.6235	$86.62	$86.60	$86.60
Purchase #5	$33.39	6.648%	$35.6098	$35.61	$35.60	$35.60
Purchase #6	$179.86	10.798%	$199.2813	$199.28	$199.30	$199.30
Purchase #7	$50.37	8.262%	$54.5316	$54.53	$54.55	$54.50
7 purchase totals =	$764.66		$822.0828	$822.08	$822.10	$822.10