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	$52.38	4.219%	$54.5899	$54.59	$54.60	$54.60
Purchase #2	$215.25	11.190%	$239.3365	$239.34	$239.35	$239.30
Purchase #3	$94.27	5.500%	$99.4549	$99.45	$99.45	$99.50
Purchase #4	$21.94	13.650%	$24.9348	$24.93	$24.95	$24.90
Purchase #5	$92.30	4.545%	$96.495	$96.50	$96.50	$96.50
Purchase #6	$192.73	10.429%	$212.8298	$212.83	$212.85	$212.80
Purchase #7	$250.56	10.322%	$276.4228	$276.42	$276.40	$276.40
7 purchase totals =	$919.43		$1,004.0637	$1,004.06	$1,004.10	$1,004.00