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	$52.68	3.561%	$54.5559	$54.56	$54.55	$54.60
Purchase #2	$194.80	10.450%	$215.1566	$215.16	$215.15	$215.20
Purchase #3	$18.56	3.366%	$19.1847	$19.18	$19.20	$19.20
Purchase #4	$233.87	13.243%	$264.8414	$264.84	$264.85	$264.80
Purchase #5	$26.76	9.588%	$29.3257	$29.33	$29.35	$29.30
Purchase #6	$239.47	9.149%	$261.3791	$261.38	$261.40	$261.40
Purchase #7	$163.28	5.432%	$172.1494	$172.15	$172.15	$172.10
7 purchase totals =	$929.42		$1,016.5928	$1,016.60	$1,016.65	$1,016.60