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	$89.72	12.283%	$100.7403	$100.74	$100.75	$100.70
Purchase #2	$128.49	8.291%	$139.1431	$139.14	$139.15	$139.10
Purchase #3	$51.88	4.792%	$54.3661	$54.37	$54.35	$54.40
Purchase #4	$46.89	11.787%	$52.4169	$52.42	$52.40	$52.40
Purchase #5	$9.28	8.424%	$10.0617	$10.06	$10.05	$10.10
Purchase #6	$35.98	12.808%	$40.5883	$40.59	$40.60	$40.60
Purchase #7	$42.80	10.785%	$47.416	$47.42	$47.40	$47.40
7 purchase totals =	$405.04		$444.7324	$444.74	$444.70	$444.70