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	$102.58	13.116%	$116.0344	$116.03	$116.05	$116.00
Purchase #2	$77.68	6.621%	$82.8232	$82.82	$82.80	$82.80
Purchase #3	$215.87	12.870%	$243.6525	$243.65	$243.65	$243.70
Purchase #4	$155.27	10.504%	$171.5796	$171.58	$171.60	$171.60
Purchase #5	$165.36	6.265%	$175.7198	$175.72	$175.70	$175.70
Purchase #6	$140.98	7.145%	$151.053	$151.05	$151.05	$151.10
Purchase #7	$217.58	12.636%	$245.0734	$245.07	$245.05	$245.10
7 purchase totals =	$1,075.32		$1,185.9359	$1,185.92	$1,185.90	$1,186.00