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	$140.65	10.470%	$155.3761	$155.38	$155.40	$155.40
Purchase #2	$185.42	12.871%	$209.2854	$209.29	$209.30	$209.30
Purchase #3	$177.47	4.684%	$185.7827	$185.78	$185.80	$185.80
Purchase #4	$235.78	7.150%	$252.6383	$252.64	$252.65	$252.60
Purchase #5	$76.42	12.539%	$86.0023	$86.00	$86.00	$86.00
Purchase #6	$55.86	12.275%	$62.7168	$62.72	$62.70	$62.70
Purchase #7	$147.95	3.218%	$152.711	$152.71	$152.70	$152.70
7 purchase totals =	$1,019.55		$1,104.5126	$1,104.52	$1,104.55	$1,104.50