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	$159.40	3.816%	$165.4827	$165.48	$165.50	$165.50
Purchase #2	$214.54	11.844%	$239.9501	$239.95	$239.95	$240.00
Purchase #3	$20.28	8.224%	$21.9478	$21.95	$21.95	$21.90
Purchase #4	$188.45	12.662%	$212.3115	$212.31	$212.30	$212.30
Purchase #5	$213.39	12.112%	$239.2358	$239.24	$239.25	$239.20
Purchase #6	$122.79	11.325%	$136.696	$136.70	$136.70	$136.70
Purchase #7	$101.76	9.710%	$111.6409	$111.64	$111.65	$111.60
7 purchase totals =	$1,020.61		$1,127.2648	$1,127.27	$1,127.30	$1,127.20