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	$193.50	12.704%	$218.0822	$218.08	$218.10	$218.10
Purchase #2	$247.86	12.182%	$278.0543	$278.05	$278.05	$278.10
Purchase #3	$18.50	4.813%	$19.3904	$19.39	$19.40	$19.40
Purchase #4	$53.75	10.344%	$59.3099	$59.31	$59.30	$59.30
Purchase #5	$162.60	12.690%	$183.2339	$183.23	$183.25	$183.20
Purchase #6	$99.83	7.617%	$107.4341	$107.43	$107.45	$107.40
Purchase #7	$135.52	4.825%	$142.0588	$142.06	$142.05	$142.10
7 purchase totals =	$911.56		$1,007.5636	$1,007.55	$1,007.60	$1,007.60