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	$48.51	10.459%	$53.5837	$53.58	$53.60	$53.60
Purchase #2	$248.83	13.217%	$281.7179	$281.72	$281.70	$281.70
Purchase #3	$158.65	6.456%	$168.8924	$168.89	$168.90	$168.90
Purchase #4	$114.72	13.326%	$130.0076	$130.01	$130.00	$130.00
Purchase #5	$26.73	11.312%	$29.7537	$29.75	$29.75	$29.80
Purchase #6	$215.42	4.475%	$225.06	$225.06	$225.05	$225.10
Purchase #7	$111.46	4.273%	$116.2227	$116.22	$116.20	$116.20
7 purchase totals =	$924.32		$1,005.2380	$1,005.23	$1,005.20	$1,005.30