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	$183.44	12.705%	$206.7461	$206.75	$206.75	$206.70
Purchase #2	$149.51	4.226%	$155.8283	$155.83	$155.85	$155.80
Purchase #3	$63.81	13.491%	$72.4186	$72.42	$72.40	$72.40
Purchase #4	$247.97	6.622%	$264.3906	$264.39	$264.40	$264.40
Purchase #5	$80.96	4.753%	$84.808	$84.81	$84.80	$84.80
Purchase #6	$106.25	5.318%	$111.9004	$111.90	$111.90	$111.90
Purchase #7	$249.94	10.379%	$275.8813	$275.88	$275.90	$275.90
7 purchase totals =	$1,081.88		$1,171.9733	$1,171.98	$1,172.00	$1,171.90