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	$224.83	5.380%	$236.9259	$236.93	$236.95	$236.90
Purchase #2	$128.28	8.847%	$139.6289	$139.63	$139.65	$139.60
Purchase #3	$209.60	4.155%	$218.3089	$218.31	$218.30	$218.30
Purchase #4	$109.29	10.342%	$120.5928	$120.59	$120.60	$120.60
Purchase #5	$100.51	7.789%	$108.3387	$108.34	$108.35	$108.30
Purchase #6	$48.53	4.517%	$50.7221	$50.72	$50.70	$50.70
Purchase #7	$244.38	8.491%	$265.1303	$265.13	$265.15	$265.10
7 purchase totals =	$1,065.42		$1,139.6476	$1,139.65	$1,139.70	$1,139.50