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	$154.76	4.730%	$162.0801	$162.08	$162.10	$162.10
Purchase #2	$43.89	9.569%	$48.0898	$48.09	$48.10	$48.10
Purchase #3	$17.74	4.584%	$18.5532	$18.55	$18.55	$18.60
Purchase #4	$214.91	13.313%	$243.521	$243.52	$243.50	$243.50
Purchase #5	$43.54	8.357%	$47.1786	$47.18	$47.20	$47.20
Purchase #6	$167.86	10.718%	$185.8512	$185.85	$185.85	$185.90
Purchase #7	$50.31	6.331%	$53.4951	$53.50	$53.50	$53.50
7 purchase totals =	$693.01		$758.7690	$758.77	$758.80	$758.90