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	$104.60	6.139%	$111.0214	$111.02	$111.00	$111.00
Purchase #2	$207.68	4.854%	$217.7608	$217.76	$217.75	$217.80
Purchase #3	$35.83	5.598%	$37.8358	$37.84	$37.85	$37.80
Purchase #4	$228.30	3.148%	$235.4869	$235.49	$235.50	$235.50
Purchase #5	$128.96	10.179%	$142.0868	$142.09	$142.10	$142.10
Purchase #6	$46.37	5.247%	$48.803	$48.80	$48.80	$48.80
Purchase #7	$136.84	7.145%	$146.6172	$146.62	$146.60	$146.60
7 purchase totals =	$888.58		$939.6119	$939.62	$939.60	$939.60