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	$56.56	10.542%	$62.5226	$62.52	$62.50	$62.50
Purchase #2	$134.64	3.406%	$139.2258	$139.23	$139.25	$139.20
Purchase #3	$170.59	8.824%	$185.6429	$185.64	$185.65	$185.60
Purchase #4	$29.86	8.154%	$32.2948	$32.29	$32.30	$32.30
Purchase #5	$182.54	4.326%	$190.4367	$190.44	$190.45	$190.40
Purchase #6	$238.79	5.604%	$252.1718	$252.17	$252.15	$252.20
Purchase #7	$142.62	7.801%	$153.7458	$153.75	$153.75	$153.70
7 purchase totals =	$955.60		$1,016.0404	$1,016.04	$1,016.05	$1,015.90