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	$245.89	6.131%	$260.9655	$260.97	$260.95	$261.00
Purchase #2	$175.75	5.672%	$185.7185	$185.72	$185.70	$185.70
Purchase #3	$36.56	6.521%	$38.9441	$38.94	$38.95	$38.90
Purchase #4	$225.63	4.841%	$236.5527	$236.55	$236.55	$236.60
Purchase #5	$174.62	5.340%	$183.9447	$183.94	$183.95	$183.90
Purchase #6	$86.77	4.433%	$90.6165	$90.62	$90.60	$90.60
Purchase #7	$116.86	12.178%	$131.0912	$131.09	$131.10	$131.10
7 purchase totals =	$1,062.08		$1,127.8332	$1,127.83	$1,127.80	$1,127.80