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	$80.90	5.815%	$85.6043	$85.60	$85.60	$85.60
Purchase #2	$128.67	12.469%	$144.7139	$144.71	$144.70	$144.70
Purchase #3	$22.39	13.591%	$25.433	$25.43	$25.45	$25.40
Purchase #4	$57.86	6.754%	$61.7679	$61.77	$61.75	$61.80
Purchase #5	$173.36	3.260%	$179.0115	$179.01	$179.00	$179.00
Purchase #6	$155.91	4.289%	$162.597	$162.60	$162.60	$162.60
Purchase #7	$96.87	11.318%	$107.8337	$107.83	$107.85	$107.80
7 purchase totals =	$715.96		$766.9613	$766.95	$766.95	$766.90