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	$84.35	9.859%	$92.6661	$92.67	$92.65	$92.70
Purchase #2	$108.96	3.115%	$112.3541	$112.35	$112.35	$112.40
Purchase #3	$25.68	10.777%	$28.4475	$28.45	$28.45	$28.40
Purchase #4	$88.28	3.758%	$91.5976	$91.60	$91.60	$91.60
Purchase #5	$145.60	4.146%	$151.6366	$151.64	$151.65	$151.60
Purchase #6	$185.46	6.858%	$198.1788	$198.18	$198.20	$198.20
Purchase #7	$94.89	10.130%	$104.5024	$104.50	$104.50	$104.50
7 purchase totals =	$733.22		$779.3831	$779.39	$779.40	$779.40