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	$81.91	4.342%	$85.4665	$85.47	$85.45	$85.50
Purchase #2	$87.43	9.656%	$95.8722	$95.87	$95.85	$95.90
Purchase #3	$81.58	11.149%	$90.6754	$90.68	$90.70	$90.70
Purchase #4	$222.43	10.178%	$245.0689	$245.07	$245.05	$245.10
Purchase #5	$25.66	9.526%	$28.1044	$28.10	$28.10	$28.10
Purchase #6	$151.92	4.619%	$158.9372	$158.94	$158.95	$158.90
Purchase #7	$80.30	13.730%	$91.3252	$91.33	$91.35	$91.30
7 purchase totals =	$731.23		$795.4498	$795.46	$795.45	$795.50