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	$239.27	12.512%	$269.2075	$269.21	$269.20	$269.20
Purchase #2	$97.53	6.618%	$103.9845	$103.98	$104.00	$104.00
Purchase #3	$81.69	8.137%	$88.3371	$88.34	$88.35	$88.30
Purchase #4	$229.62	11.553%	$256.148	$256.15	$256.15	$256.10
Purchase #5	$164.70	5.820%	$174.2855	$174.29	$174.30	$174.30
Purchase #6	$104.37	7.688%	$112.394	$112.39	$112.40	$112.40
Purchase #7	$53.60	13.103%	$60.6232	$60.62	$60.60	$60.60
7 purchase totals =	$970.78		$1,064.9798	$1,064.98	$1,065.00	$1,064.90