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	$110.91	3.525%	$114.8196	$114.82	$114.80	$114.80
Purchase #2	$178.50	9.159%	$194.8488	$194.85	$194.85	$194.80
Purchase #3	$93.29	6.628%	$99.4733	$99.47	$99.45	$99.50
Purchase #4	$39.66	13.270%	$44.9229	$44.92	$44.90	$44.90
Purchase #5	$97.85	13.436%	$110.9971	$111.00	$111.00	$111.00
Purchase #6	$158.73	12.620%	$178.7617	$178.76	$178.75	$178.80
Purchase #7	$12.67	13.356%	$14.3622	$14.36	$14.35	$14.40
7 purchase totals =	$691.61		$758.1856	$758.18	$758.10	$758.20