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	$213.30	13.679%	$242.4773	$242.48	$242.50	$242.50
Purchase #2	$100.33	4.793%	$105.1388	$105.14	$105.15	$105.10
Purchase #3	$100.30	10.744%	$111.0762	$111.08	$111.10	$111.10
Purchase #4	$146.69	7.358%	$157.4835	$157.48	$157.50	$157.50
Purchase #5	$221.37	6.435%	$235.6152	$235.62	$235.60	$235.60
Purchase #6	$126.69	9.717%	$139.0005	$139.00	$139.00	$139.00
Purchase #7	$227.97	9.792%	$250.2928	$250.29	$250.30	$250.30
7 purchase totals =	$1,136.65		$1,241.0843	$1,241.09	$1,241.15	$1,241.10