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	$218.54	6.668%	$233.1122	$233.11	$233.10	$233.10
Purchase #2	$8.28	12.382%	$9.3052	$9.31	$9.30	$9.30
Purchase #3	$147.63	7.355%	$158.4882	$158.49	$158.50	$158.50
Purchase #4	$142.91	5.347%	$150.5514	$150.55	$150.55	$150.60
Purchase #5	$248.83	5.617%	$262.8068	$262.81	$262.80	$262.80
Purchase #6	$38.82	12.266%	$43.5817	$43.58	$43.60	$43.60
Purchase #7	$140.71	12.504%	$158.3044	$158.30	$158.30	$158.30
7 purchase totals =	$945.72		$1,016.1499	$1,016.15	$1,016.15	$1,016.20