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	$247.85	6.567%	$264.1263	$264.13	$264.15	$264.10
Purchase #2	$196.89	5.356%	$207.4354	$207.44	$207.45	$207.40
Purchase #3	$215.87	10.188%	$237.8628	$237.86	$237.85	$237.90
Purchase #4	$117.95	7.827%	$127.1819	$127.18	$127.20	$127.20
Purchase #5	$245.71	9.758%	$269.6864	$269.69	$269.70	$269.70
Purchase #6	$159.78	4.688%	$167.2705	$167.27	$167.25	$167.30
Purchase #7	$111.92	10.634%	$123.8216	$123.82	$123.80	$123.80
7 purchase totals =	$1,295.97		$1,397.3849	$1,397.39	$1,397.40	$1,397.40