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	$104.65	12.798%	$118.0431	$118.04	$118.05	$118.00
Purchase #2	$179.85	5.413%	$189.5853	$189.59	$189.60	$189.60
Purchase #3	$207.40	8.608%	$225.253	$225.25	$225.25	$225.30
Purchase #4	$18.92	7.273%	$20.2961	$20.30	$20.30	$20.30
Purchase #5	$142.80	8.779%	$155.3364	$155.34	$155.35	$155.30
Purchase #6	$164.97	12.328%	$185.3075	$185.31	$185.30	$185.30
Purchase #7	$131.75	11.335%	$146.6839	$146.68	$146.70	$146.70
7 purchase totals =	$950.34		$1,040.5053	$1,040.51	$1,040.55	$1,040.50