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	$225.93	7.510%	$242.8973	$242.90	$242.90	$242.90
Purchase #2	$199.41	3.425%	$206.2398	$206.24	$206.25	$206.20
Purchase #3	$19.25	12.618%	$21.679	$21.68	$21.70	$21.70
Purchase #4	$154.30	11.665%	$172.2991	$172.30	$172.30	$172.30
Purchase #5	$68.64	5.145%	$72.1715	$72.17	$72.15	$72.20
Purchase #6	$53.56	5.473%	$56.4913	$56.49	$56.50	$56.50
Purchase #7	$111.65	11.622%	$124.626	$124.63	$124.65	$124.60
7 purchase totals =	$832.74		$896.4040	$896.41	$896.45	$896.40