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	$246.45	5.421%	$259.8101	$259.81	$259.80	$259.80
Purchase #2	$27.61	6.233%	$29.3309	$29.33	$29.35	$29.30
Purchase #3	$64.59	3.507%	$66.8552	$66.86	$66.85	$66.90
Purchase #4	$239.60	3.580%	$248.1777	$248.18	$248.20	$248.20
Purchase #5	$37.50	13.225%	$42.4594	$42.46	$42.45	$42.50
Purchase #6	$193.25	3.566%	$200.1413	$200.14	$200.15	$200.10
Purchase #7	$248.49	8.476%	$269.552	$269.55	$269.55	$269.60
7 purchase totals =	$1,057.49		$1,116.3266	$1,116.33	$1,116.35	$1,116.40