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	$40.71	11.655%	$45.4548	$45.45	$45.45	$45.50
Purchase #2	$140.27	8.189%	$151.7567	$151.76	$151.75	$151.80
Purchase #3	$39.28	3.275%	$40.5664	$40.57	$40.55	$40.60
Purchase #4	$107.33	3.812%	$111.4214	$111.42	$111.40	$111.40
Purchase #5	$241.92	10.528%	$267.3893	$267.39	$267.40	$267.40
Purchase #6	$200.30	9.787%	$219.9034	$219.90	$219.90	$219.90
Purchase #7	$168.87	5.849%	$178.7472	$178.75	$178.75	$178.70
7 purchase totals =	$938.68		$1,015.2392	$1,015.24	$1,015.20	$1,015.30