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	$66.75	10.741%	$73.9196	$73.92	$73.90	$73.90
Purchase #2	$228.80	13.351%	$259.3471	$259.35	$259.35	$259.30
Purchase #3	$224.63	6.789%	$239.8801	$239.88	$239.90	$239.90
Purchase #4	$134.25	11.778%	$150.062	$150.06	$150.05	$150.10
Purchase #5	$127.69	3.236%	$131.822	$131.82	$131.80	$131.80
Purchase #6	$175.92	13.257%	$199.2417	$199.24	$199.25	$199.20
Purchase #7	$11.92	11.407%	$13.2797	$13.28	$13.30	$13.30
7 purchase totals =	$969.96		$1,067.5522	$1,067.55	$1,067.55	$1,067.50