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	$191.92	8.773%	$208.7571	$208.76	$208.75	$208.80
Purchase #2	$168.38	7.164%	$180.4427	$180.44	$180.45	$180.40
Purchase #3	$143.75	5.667%	$151.8963	$151.90	$151.90	$151.90
Purchase #4	$123.88	12.513%	$139.3811	$139.38	$139.40	$139.40
Purchase #5	$127.30	9.581%	$139.4966	$139.50	$139.50	$139.50
Purchase #6	$104.55	11.564%	$116.6402	$116.64	$116.65	$116.60
Purchase #7	$163.65	10.252%	$180.4274	$180.43	$180.45	$180.40
7 purchase totals =	$1,023.43		$1,117.0414	$1,117.05	$1,117.10	$1,117.00