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	$149.48	13.416%	$169.5342	$169.53	$169.55	$169.50
Purchase #2	$55.81	12.563%	$62.8214	$62.82	$62.80	$62.80
Purchase #3	$90.91	4.768%	$95.2446	$95.24	$95.25	$95.20
Purchase #4	$69.92	10.372%	$77.1721	$77.17	$77.15	$77.20
Purchase #5	$178.62	10.108%	$196.6749	$196.67	$196.65	$196.70
Purchase #6	$35.51	8.227%	$38.4314	$38.43	$38.45	$38.40
Purchase #7	$199.77	3.280%	$206.3225	$206.32	$206.30	$206.30
7 purchase totals =	$780.02		$846.2011	$846.18	$846.15	$846.10