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	$237.79	9.151%	$259.5502	$259.55	$259.55	$259.60
Purchase #2	$154.64	11.133%	$171.8561	$171.86	$171.85	$171.90
Purchase #3	$57.31	4.240%	$59.7399	$59.74	$59.75	$59.70
Purchase #4	$215.75	10.648%	$238.7231	$238.72	$238.70	$238.70
Purchase #5	$74.73	8.791%	$81.2995	$81.30	$81.30	$81.30
Purchase #6	$145.25	5.746%	$153.5961	$153.60	$153.60	$153.60
Purchase #7	$62.40	9.363%	$68.2425	$68.24	$68.25	$68.20
7 purchase totals =	$947.87		$1,033.0074	$1,033.01	$1,033.00	$1,033.00