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	$72.81	5.763%	$77.006	$77.01	$77.00	$77.00
Purchase #2	$38.59	6.110%	$40.9478	$40.95	$40.95	$40.90
Purchase #3	$104.30	10.748%	$115.5102	$115.51	$115.50	$115.50
Purchase #4	$42.57	12.757%	$48.0007	$48.00	$48.00	$48.00
Purchase #5	$212.28	9.808%	$233.1004	$233.10	$233.10	$233.10
Purchase #6	$129.82	13.682%	$147.582	$147.58	$147.60	$147.60
Purchase #7	$206.52	7.755%	$222.5356	$222.54	$222.55	$222.50
7 purchase totals =	$806.89		$884.6827	$884.69	$884.70	$884.60