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	$198.72	3.313%	$205.3036	$205.30	$205.30	$205.30
Purchase #2	$181.84	3.268%	$187.7825	$187.78	$187.80	$187.80
Purchase #3	$130.40	9.712%	$143.0644	$143.06	$143.05	$143.10
Purchase #4	$118.38	7.572%	$127.3437	$127.34	$127.35	$127.30
Purchase #5	$196.71	12.475%	$221.2496	$221.25	$221.25	$221.20
Purchase #6	$41.47	8.839%	$45.1355	$45.14	$45.15	$45.10
Purchase #7	$78.87	9.272%	$86.1828	$86.18	$86.20	$86.20
7 purchase totals =	$946.39		$1,016.0621	$1,016.05	$1,016.10	$1,016.00