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	$206.72	4.447%	$215.9128	$215.91	$215.90	$215.90
Purchase #2	$105.26	13.605%	$119.5806	$119.58	$119.60	$119.60
Purchase #3	$24.26	6.418%	$25.817	$25.82	$25.80	$25.80
Purchase #4	$51.58	8.358%	$55.8911	$55.89	$55.90	$55.90
Purchase #5	$41.26	9.392%	$45.1351	$45.14	$45.15	$45.10
Purchase #6	$200.39	8.178%	$216.7779	$216.78	$216.80	$216.80
Purchase #7	$164.85	4.868%	$172.8749	$172.87	$172.85	$172.90
7 purchase totals =	$794.32		$851.9894	$851.99	$852.00	$852.00