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	$228.66	4.782%	$239.5945	$239.59	$239.60	$239.60
Purchase #2	$91.37	12.798%	$103.0635	$103.06	$103.05	$103.10
Purchase #3	$47.78	9.183%	$52.1676	$52.17	$52.15	$52.20
Purchase #4	$145.44	3.481%	$150.5028	$150.50	$150.50	$150.50
Purchase #5	$212.40	5.355%	$223.774	$223.77	$223.75	$223.80
Purchase #6	$156.31	13.429%	$177.3009	$177.30	$177.30	$177.30
Purchase #7	$54.42	9.326%	$59.4952	$59.50	$59.50	$59.50
7 purchase totals =	$936.38		$1,005.8985	$1,005.89	$1,005.85	$1,006.00