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	$167.51	6.624%	$178.6059	$178.61	$178.60	$178.60
Purchase #2	$100.79	9.711%	$110.5777	$110.58	$110.60	$110.60
Purchase #3	$46.55	4.602%	$48.6922	$48.69	$48.70	$48.70
Purchase #4	$84.56	5.839%	$89.4975	$89.50	$89.50	$89.50
Purchase #5	$128.66	8.668%	$139.8122	$139.81	$139.80	$139.80
Purchase #6	$234.71	8.120%	$253.7685	$253.77	$253.75	$253.80
Purchase #7	$193.85	10.164%	$213.5529	$213.55	$213.55	$213.60
7 purchase totals =	$956.63		$1,034.5069	$1,034.51	$1,034.50	$1,034.60