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	$52.90	3.558%	$54.7822	$54.78	$54.80	$54.80
Purchase #2	$203.56	3.504%	$210.6927	$210.69	$210.70	$210.70
Purchase #3	$220.62	7.470%	$237.1003	$237.10	$237.10	$237.10
Purchase #4	$191.52	9.551%	$209.8121	$209.81	$209.80	$209.80
Purchase #5	$52.69	6.724%	$56.2329	$56.23	$56.25	$56.20
Purchase #6	$61.95	13.451%	$70.2829	$70.28	$70.30	$70.30
Purchase #7	$195.41	13.688%	$222.1577	$222.16	$222.15	$222.20
7 purchase totals =	$978.65		$1,061.0608	$1,061.05	$1,061.10	$1,061.10