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	$44.70	6.168%	$47.4571	$47.46	$47.45	$47.50
Purchase #2	$227.79	3.411%	$235.5599	$235.56	$235.55	$235.60
Purchase #3	$48.62	11.487%	$54.205	$54.21	$54.20	$54.20
Purchase #4	$233.31	9.386%	$255.2085	$255.21	$255.20	$255.20
Purchase #5	$35.51	4.254%	$37.0206	$37.02	$37.00	$37.00
Purchase #6	$86.59	4.839%	$90.7801	$90.78	$90.80	$90.80
Purchase #7	$11.33	8.339%	$12.2748	$12.27	$12.25	$12.30
7 purchase totals =	$687.85		$732.5060	$732.51	$732.45	$732.60