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	$183.78	11.680%	$205.2455	$205.25	$205.25	$205.20
Purchase #2	$198.52	13.360%	$225.0423	$225.04	$225.05	$225.00
Purchase #3	$51.31	6.257%	$54.5205	$54.52	$54.50	$54.50
Purchase #4	$202.75	10.640%	$224.3226	$224.32	$224.30	$224.30
Purchase #5	$89.52	9.373%	$97.9107	$97.91	$97.90	$97.90
Purchase #6	$70.90	9.157%	$77.3923	$77.39	$77.40	$77.40
Purchase #7	$166.72	12.404%	$187.3999	$187.40	$187.40	$187.40
7 purchase totals =	$963.50		$1,071.8338	$1,071.83	$1,071.80	$1,071.70