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	$244.66	4.829%	$256.4746	$256.47	$256.45	$256.50
Purchase #2	$14.47	5.317%	$15.2394	$15.24	$15.25	$15.20
Purchase #3	$246.52	13.104%	$278.824	$278.82	$278.80	$278.80
Purchase #4	$205.61	9.475%	$225.0915	$225.09	$225.10	$225.10
Purchase #5	$78.92	13.160%	$89.3059	$89.31	$89.30	$89.30
Purchase #6	$169.33	8.232%	$183.2692	$183.27	$183.25	$183.30
Purchase #7	$205.62	3.788%	$213.4089	$213.41	$213.40	$213.40
7 purchase totals =	$1,165.13		$1,261.6135	$1,261.61	$1,261.55	$1,261.60