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	$209.73	6.444%	$223.245	$223.25	$223.25	$223.20
Purchase #2	$174.90	9.208%	$191.0048	$191.00	$191.00	$191.00
Purchase #3	$158.63	12.723%	$178.8125	$178.81	$178.80	$178.80
Purchase #4	$193.85	10.547%	$214.2954	$214.30	$214.30	$214.30
Purchase #5	$38.33	12.287%	$43.0396	$43.04	$43.05	$43.00
Purchase #6	$91.97	7.109%	$98.5081	$98.51	$98.50	$98.50
Purchase #7	$98.50	12.861%	$111.1681	$111.17	$111.15	$111.20
7 purchase totals =	$965.91		$1,060.0735	$1,060.08	$1,060.05	$1,060.00