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	$181.90	12.796%	$205.1759	$205.18	$205.20	$205.20
Purchase #2	$245.35	13.564%	$278.6293	$278.63	$278.65	$278.60
Purchase #3	$46.47	13.457%	$52.7235	$52.72	$52.70	$52.70
Purchase #4	$43.96	3.585%	$45.536	$45.54	$45.55	$45.50
Purchase #5	$143.68	12.244%	$161.2722	$161.27	$161.25	$161.30
Purchase #6	$209.51	8.603%	$227.5341	$227.53	$227.55	$227.50
Purchase #7	$101.65	12.559%	$114.4162	$114.42	$114.40	$114.40
7 purchase totals =	$972.52		$1,085.2872	$1,085.29	$1,085.30	$1,085.20