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	$205.62	6.542%	$219.0717	$219.07	$219.05	$219.10
Purchase #2	$48.82	11.841%	$54.6008	$54.60	$54.60	$54.60
Purchase #3	$221.60	9.733%	$243.1683	$243.17	$243.15	$243.20
Purchase #4	$101.34	10.334%	$111.8125	$111.81	$111.80	$111.80
Purchase #5	$32.69	7.592%	$35.1718	$35.17	$35.15	$35.20
Purchase #6	$249.89	7.670%	$269.0566	$269.06	$269.05	$269.10
Purchase #7	$201.28	5.868%	$213.0911	$213.09	$213.10	$213.10
7 purchase totals =	$1,061.24		$1,145.9728	$1,145.97	$1,145.90	$1,146.10