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	$221.27	13.261%	$250.6126	$250.61	$250.60	$250.60
Purchase #2	$45.77	6.617%	$48.7986	$48.80	$48.80	$48.80
Purchase #3	$241.44	6.859%	$258.0004	$258.00	$258.00	$258.00
Purchase #4	$84.42	10.159%	$92.9962	$93.00	$93.00	$93.00
Purchase #5	$142.42	4.127%	$148.2977	$148.30	$148.30	$148.30
Purchase #6	$97.73	9.164%	$106.686	$106.69	$106.70	$106.70
Purchase #7	$136.74	13.800%	$155.6101	$155.61	$155.60	$155.60
7 purchase totals =	$969.79		$1,061.0016	$1,061.01	$1,061.00	$1,061.00