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	$163.56	8.608%	$177.6392	$177.64	$177.65	$177.60
Purchase #2	$148.33	5.230%	$156.0877	$156.09	$156.10	$156.10
Purchase #3	$134.41	3.480%	$139.0875	$139.09	$139.10	$139.10
Purchase #4	$85.69	5.674%	$90.5521	$90.55	$90.55	$90.60
Purchase #5	$63.64	6.594%	$67.8364	$67.84	$67.85	$67.80
Purchase #6	$17.89	4.815%	$18.7514	$18.75	$18.75	$18.80
Purchase #7	$120.45	5.519%	$127.0976	$127.10	$127.10	$127.10
7 purchase totals =	$733.97		$777.0519	$777.06	$777.10	$777.10