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	$71.59	10.224%	$78.9094	$78.91	$78.90	$78.90
Purchase #2	$38.30	12.526%	$43.0975	$43.10	$43.10	$43.10
Purchase #3	$16.81	13.846%	$19.1375	$19.14	$19.15	$19.10
Purchase #4	$246.82	7.238%	$264.6848	$264.68	$264.70	$264.70
Purchase #5	$246.52	3.864%	$256.0455	$256.05	$256.05	$256.00
Purchase #6	$89.99	11.590%	$100.4198	$100.42	$100.40	$100.40
Purchase #7	$210.45	12.784%	$237.3539	$237.35	$237.35	$237.40
7 purchase totals =	$920.48		$999.6484	$999.65	$999.65	$999.60