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	$209.69	13.181%	$237.3292	$237.33	$237.35	$237.30
Purchase #2	$120.86	7.798%	$130.2847	$130.28	$130.30	$130.30
Purchase #3	$48.27	5.561%	$50.9543	$50.95	$50.95	$51.00
Purchase #4	$74.80	10.839%	$82.9076	$82.91	$82.90	$82.90
Purchase #5	$159.69	4.240%	$166.4609	$166.46	$166.45	$166.50
Purchase #6	$136.39	4.778%	$142.9067	$142.91	$142.90	$142.90
Purchase #7	$229.48	12.221%	$257.5248	$257.52	$257.50	$257.50
7 purchase totals =	$979.18		$1,068.3682	$1,068.36	$1,068.35	$1,068.40