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	$205.93	12.213%	$231.0802	$231.08	$231.10	$231.10
Purchase #2	$210.36	7.552%	$226.2464	$226.25	$226.25	$226.20
Purchase #3	$104.33	4.728%	$109.2627	$109.26	$109.25	$109.30
Purchase #4	$115.83	9.756%	$127.1304	$127.13	$127.15	$127.10
Purchase #5	$141.51	10.112%	$155.8195	$155.82	$155.80	$155.80
Purchase #6	$46.36	3.718%	$48.0837	$48.08	$48.10	$48.10
Purchase #7	$106.95	11.287%	$119.0214	$119.02	$119.00	$119.00
7 purchase totals =	$931.27		$1,016.6443	$1,016.64	$1,016.65	$1,016.60